26 October
Journal Club

Tomáš Šoltinský 1.00pm   A113

28 October
Lunch Talk
Crazy atomic rockets
Julian Onions 1.00pm   TEAMS

29 October
MLiS talks
TBA
TBA 1.00pm   TEAMS

02 November
Journal Club

Mick Greener 1.00pm   A113

03 November
Weekly Seminar

Research area: [Reionisation/Lyman alpha]
Sarah Bosman (MPIA) 3.45pm   TEAMS

04 November
Lunch Talk

Liza Sazonova (John Hopkins) 1.00pm   TEAMS

09 November
Journal Club

Kellie de Vos 1.00pm   A113

10 November
Weekly Seminar

Research area: [Machine learning/AGN/galaxy evolution]
Joanna Piotrowska (Cambridge) 3.45pm   TEAMS

11 November
Lunch Talk

Margherita Molaro 1.00pm   TEAMS

12 November
MLiS talks
The application of deep learning on image quality assessment and ISP auto tuning
Xiaoyu Wu (Huawei) 1.00pm   TEAMS

17 November
Weekly Seminar

Research area: [Reionisation/21cm]
Emma Chapman (Nottingham) 3.45pm   TEAMS

18 November
Lunch Talk

Lizzie Taylor 1.00pm   TEAMS

23 November
Journal Club

Roan Haggar 1.00pm   A113

25 November
Lunch Talk

Roan Haggar 1.00pm   TEAMS

26 November
MLiS talks

Alessio Mancini (UCL) 1.00pm   TEAMS

30 November
Journal Club

Lizzie Taylor 1.00pm   A113

01 December
Weekly Seminar

Research area: [Galaxy Structure/star clusters/simulations]
Sebastian Trujillo-Gomez (Heidelberg) 3.45pm   TEAMS

07 December
Journal Club

Leonardo de Albernaz Ferreira 1.00pm   A113

08 December
Weekly Seminar

Research area: [Bayesian stats/exoplanets]
David Hogg (NYU) 3.45pm   TEAMS

09 December
Lunch Talk

Karel Green 1.00pm   TEAMS

10 December
MLiS talks
The Rise of Artificial Intelligence for Space Applications
Bertrand Le Saux & Pierre-Philippe Mathieu (European Space Agency) 1.00pm   TEAMS

15 December
Weekly Seminar

Research area: [Cosmo simulations/Galaxy formation/low surface-brightness]
Gareth Martin (Korea Astronomy and Space Science Institute) 3.45pm   TEAMS

13 January
Lunch Talk

Jacob Maresca 1.00pm   TEAMS

14 January
MLiS talks

TBA 1.00pm   TEAMS

20 January
Lunch Talk

Marta Ramos (St Andrews) 1.00pm   TEAMS

27 January
Lunch Talk

Aneesh Naik 1.00pm   TEAMS

28 January
MLiS talks

TBA 1.00pm   TEAMS

03 February
Lunch Talk

Ryan Begley (Edinburgh) 1.00pm   TEAMS

10 February
Lunch Talk

Anshu Gupta (Curtin Institute for Radio Astronomy) 1.00pm   TEAMS

11 February
MLiS talks

TBA 1.00pm   TEAMS

17 February
Lunch Talk

Tomáš Šoltinský 1.00pm   TEAMS

25 February
MLiS talks

TBA 1.00pm   TEAMS

03 March
Lunch Talk

Leonardo de Albernaz Ferreira 1.00pm   TEAMS

11 March
MLiS talks

TBA 1.00pm   TEAMS

17 March
Lunch Talk

Alfonso Aragón-Salamanca 1.00pm   TEAMS

24 March
Lunch Talk

Ulli Kuchner 1.00pm   TEAMS

07 April
Lunch Talk

Stephane Werner 1.00pm   TEAMS

05 May
Lunch Talk

Dan Cornwell 1.00pm   TEAMS

12 May
Lunch Talk

Kellie de Vos 1.00pm   TEAMS

Unless stated otherwise the seminars take place in Physics C12 at 15:45 with the student session in CAPT A113 at 15:00. Click on an event for more information.

Event organiser:  Margherita Molaro and Shaun Read

03 Nov
Title TBC
Sarah Bosman (MPIA)
3.45pm  TEAMS
Research area: [Reionisation/Lyman alpha]

10 Nov
Title TBC
Joanna Piotrowska (Cambridge)
3.45pm  TEAMS
Research area: [Machine learning/AGN/galaxy evolution]

17 Nov
Title TBC
Emma Chapman (Nottingham)
3.45pm  TEAMS
Research area: [Reionisation/21cm]

01 Dec
Title TBC
Sebastian Trujillo-Gomez (Heidelberg)
3.45pm  TEAMS
Research area: [Galaxy Structure/star clusters/simulations]

08 Dec
Title TBC
David Hogg (NYU)
3.45pm  TEAMS
Research area: [Bayesian stats/exoplanets]

15 Dec
Title TBC
Gareth Martin (Korea Astronomy and Space Science Institute)
3.45pm  TEAMS
Research area: [Cosmo simulations/Galaxy formation/low surface-brightness]

22 Sep
Studying the formation of giant clumps in high redshift galaxies using Machine Learning
Marc Huertas-Company (University of California)
3.45pm  TEAMS
Research area: [Machine learning/star-formation]

In this talk I will first present a new automated method based on deep neural networks to detect clumps in galaxy images. I will show that the method is both faster and more sensitive than previous published approaches. I will then show how we use the new method to perform for the first time a systematic detection of clumps in rest-frame optical in a complete sample of ~1,500 star forming galaxies with 1<z<3 in the CANDELS survey and derive clump stellar masses through Bayesian SED fitting. The clump stellar mass functions follow a power-law with a slope of alpha=-1 to -1.5 down to the completeness limit (10^{8.5} solar masses). We find that between 20-40% of star-forming galaxies contain at least one massive off-centered clump but only ~5% of the total galaxy stellar mass is in massive clumps. I will finally show the results of a comparison with forward modeled zoom-in cosmological simulations in which most clumps are formed in-situ through gravitational instabilities. We show that observational effects have a dramatic impact on the derived clump stellar mass functions by overestimating the clump mass up to a factor of 10, which highlights the importance of fair and direct comparisons between observations and simulations and the limitations of current HST data to study the resolved structure of distant galaxies. When all the observational effects are taken into account, we show that the simulations explored in this work overall reproduce the observed clump abundances and clumpy fractions. This good agreement suggests that most of the observed clumps are formed in-situ. I will conclude by explaining how future detailed and consistent comparisons of clump properties - especially observed with JWST - with other simulated samples have the potential to put additional statistical constraints on feedback mechanisms.

29 Sep
Revealing how Galaxy Growth, Star Formation and Quenching proceed in High Redshift Galaxies with Spatially Resolved Space-based Slitless Spectroscopy
Jasleen Matharu (Texas A&M University)
3.45pm  TEAMS
Research area: [Galaxy evolution/spectroscopy/galaxy structure]

Space-based slitless spectroscopy capabilities on-board the Hubble Space Telescope have made it possible for us to conduct spatially-resolved studies of star formation in high redshift galaxies for the first time. The future is truly slitless, with the James Webb Space Telescope and the Nancy Grace Roman Space Telescope vastly improving and capitalizing on the scientific gains we will make with this mode of observation. I will begin by demonstrating how spatially resolved studies with the Hubble Space Telescope have allowed us to determine which galaxy size growth mechanisms dominate and how the quiescent (not forming stars) population of galaxies builds up with redshift. Subsequently, I will unveil the first spatially resolved H-Alpha emission line maps of cluster galaxies at z~1 from the GCLASS survey, made possible with the Wide Field Camera 3 G141 grism on-board the Hubble Space Telescope, revealing what they have taught us about the shutdown of star formation in galaxy clusters at this crucial epoch in the history of cosmic star formation. I will end by presenting deep spatially resolved H-Alpha emission line maps of CANDELS galaxies at z~0.5 from the CLEAR survey, made possible with the Wide Field Camera 3 G102 grism on-board the Hubble Space Telescope, and what these have unveiled on galaxy size growth via star formation at intermediate redshifts. By synthesizing the few existing spatially-resolved studies of High-Redshift Galaxies between 0.5<z<1.7 we now have, I will provide the first results on how star formation propagates spatially in galaxies over time.

06 Oct
Modelling and constraining cosmic reionization
Sultan Hassan (CCA)
3.45pm  TEAMS
Research area: [Galaxy evolution/Reionisation]

Reionization marks the time at which the first stars gradually reionized the Intergalactic Medium (IGM) and the Universe transitioned from highly neutral opaque to a highly ionized-transparent state. Many ongoing and upcoming surveys, such as the Low Frequency Array (LOFAR), the Hydrogen Epoch of Reionization Array (HERA) and the Square Kilometer Array (SKA), are devoted to detecting reionization on large scales in the near future. In this talk, I will present two ongoing projects targeting two different but closely related topics. The first part will focus on answering the question: does detailed astrophysics matter to model reionization on large scales? We here examine the impact of using realistic ionizing sources as identified within the state-of-the-art cosmological hydrodynamic simulations, namely Simba, on modelling reionization on cosmological scales, and compare results with the traditional simplified models of reionization. The second part will focus on answering another important question: how to extract the maximum amount of information from future reionization surveys? In this part, we assess the viability of using normalizing flows to generate HI maps conditioned on a set of astrophysical and cosmological parameters from the CAMELS simulations. We show how this method can be used to constrain parameters based on 2D mock maps, as an attempt to go beyond the power spectrum.

20 Oct
Looking at galaxy clusters with Hubble & VLT/MUSE - Constraints on Dark Matter
Mathilde Jauzac (Durham)
3.45pm  TEAMS
Research area: [Gravitational lensing/clusters/DM tests]

Residing at the vertices of this Cosmic Web, clusters grow by steady accretion of matter from the surroundings, as well as by discrete mergers with nearby groups and clusters. Supported by simulations, this scenario regarding the total mass content and distribution in filaments and clusters remains largely untested. While combining gravitational lensing regimes to map the total mass with multi-wavelength imaging and spectroscopy of clusters and their galaxies, one can thus study the dynamical scenarios in place within these objects, trace the substructures engaged in these processes, and constrain evolution and formation theories. I will present the latest results our team obtained combining VLT/MUSE and HST observations, and conclude with a quick overview of the BUFFALO survey.

05 Aug
Black Holes and Correlations: How far can we trust our scaling relations in the local universe?”
16:00  TEAMS

07 Oct
An ARTIST's view of the Epoch of Reionisation
Margherita Molaro
3.45pm  TEAMS

Thanks to upcoming experiments such as the SKA and HERA, large-scale observations of the Epoch of Reionisation (EoR) are now within reach. Developing simulations that can produce reliable forecasts for these world-class instruments is both vital and extremely challenging, due to their huge computational requirements. Semi-numerical models of the EoR, due to their unmatched speed, are generally the technique of choice when it comes to simulating EoR data on such large scales. They are, however, prone to issues relating to photon conservation, which have been shown to have a tangible effect on the predicted power spectra. In this talk, I will introduce ARTIST, a radiative transfer method which aims to resolve this conservation issue without significantly compromising the efficiency of the simulation. Such improvements represent an important step towards understanding the EoR and maximising the amount we can learn about cosmology from EoR observations.

14 Oct
Galaxies on the fast track, prospects for understanding early galaxy formation with JWST and SPICA
Pablo Pérez-González (CSIC/INTA)
16:00  TEAMS

21 Oct
The Planes of Satellite Galaxies Problem of NOVEMBER Λ CDM cosmology
Marcel Pawlowski (Leibniz-Institute for Astrophysics)
3.45pm  TEAMS

28 Oct
Hares and Hyenas in the Sky - Astronomy on the mother continent
Katrien Kolenberg (KU Leuven)
3.45pm  TEAMS

Astronomy is sometimes regarded as the mother of all sciences, dating from when the first humans tried to understand the starry night sky and its relationship with our world. Every civilisation has developed its own cosmological models and world representation based on the observation of celestial bodies.Therefore, astronomy is also deeply rooted in Africa. Today, several African countries have operating or planned optical observatories, and the Square Kilometer Array (SKA), the largest astronomical installation so far, is underway with crucial nodes in Africa. In this talk, I will talk about some projects and initiatives, initiated within the International Astronomical Union and/or by its members, focused on the development of astronomy in Africa. I will also talk about about some cultural astronomy and STE(A)M* education projects on the African continent I have been involved in.

04 Nov
Time-delay cosmography and Hubble tension
Leon Koopmans (Kapteyn Astronomical Institute Groningen)
3.45pm  TEAMS

11 Nov
Morphological transformations of galaxies in the local Universe: an observational and theoretical perspective
Camila Correa (University of Amsterdam)
3.45pm  TEAMS

18 Nov
Gravitationally lensed gravitational waves
Graham Smith (University of Birmingham)
3.45pm  TEAMS

25 Nov
Anomaly Detection in Astronomical Data using Machine Learning
Michelle Lochner (University of Western Cape)
3.45pm  TEAMS

The next generation of telescopes such as the SKA and the Vera C. Rubin Observatory will produce enormous data sets, far too large for traditional analysis techniques. Machine learning has proven invaluable in handling large data volumes and automating many tasks traditionally done by human scientists. In this talk, I will discuss how machine learning for anomaly detection can help automate the process of locating unusual astronomical objects in large datasets thus enabling new cosmic discoveries.

02 Dec
The morphology of the Local Group galaxies
Marcin Semczuk (Leicester University)
3.45pm  TEAMS

09 Dec
Environmental signatures on galaxy populations in the first massive clusters
Veronica Strazzulio (University of Trieste)
3.45pm  TEAMS

I will present results from a recent/ongoing investigation of galaxy population properties in the most distant galaxy clusters identified in the Sunyaev-Zel'dovich SPT-SZ survey. SPT-SZ identified clusters over 2500 square degrees with an approximately redshift-independent mass threshold of ~4e+14Msun from z~0.2 out to the highest redshifts where such structures exist. We have focused on the highest-redshift tail of this cluster sample, studying five systems at 1.4<~z<~1.7 among the rarest, most massive clusters known at these redshifts. Because of its selection independent of galaxy properties, this sample is particularly well suited for galaxy evolution investigations. In the context of the many studies of galaxy evolution in distant clusters, I will present our results based on dedicated HST and Spitzer follow-up observations of this cluster sample, focusing on environmental quenching and structural evolution of galaxies in the first massive cluster environments.

16 Dec
Possible explanations for the diversity of dwarf galaxy rotation curves
Kyle Oman (Durham University)
3.45pm  TEAMS

Galaxies do not evolve in isolation, but are sensitive to their local environments. Satellites in groups and clusters do not accrete fresh gas efficiently, and are subject to additional physical processes such as ram pressure from the intra-group/cluster medium, tidal stripping in the host potential, impulsive encounters with other satellites, etc. While it is clear that all these processes operate at some level, which are most important in setting the evolution of satellites as a function of their mass, their orbits, and the mass of their host is an ongoing area of research. I will present a new analysis of SDSS and ALFALFA survey data. I use a library of satellite orbits drawn from an N-body simulation to probabilistically assign satellites to orbits based on their observed offsets from their hosts in position and velocity. I then use these data to constrain a simple analytic model describing the relationship between satellites' orbital and star formation (or gas content) histories. This reveals the sequential impact of the host environment, first on the gas supply, then on the star formation rate.

13 Jan
Neutrino cosmology with the Lyman-alpha forest
Solene Chabanier (Universite' Paris-Saclay)
16:00:00  TEAMS

Neutral hydrogen in the Intergalactic Medium produces a collection of Lya absorptions, called the Lya forest, seen in the spectra of background objects. According to the common paradigm, neutral hydrogen in the IGM evolves from primordial density fluctuations in a low density and photo-ionized environment. It therefore acts as a direct tracer of Dark Matter (DM). However, it also implies that temperature and density are tightly coupled, giving rise to degeneracies between parameters describing either cosmology or the IGM thermal history. The Lya forest 1D power spectrum (P1D) is sensitive to clustering on small scales, and as such to the smoothing scale of relativistic particles. It has been used to put the strongest constraints on the sum of the neutrino masses. To infer cosmological constraints and to test our models at the percent level accuracy, the measurements need to be compared to state-of-the-art hydrodynamical simulations. We also need to refine our understanding of the impact of galactic feedbacks on the IGM temperature.

20 Jan
Exploring radio galaxies with the MIGHTEE survey
Imogen Whittam (Oxford)
3.45pm  TEAMS

MIGHTEE is a galaxy evolution survey currently underway with the MeerKAT radio telescope. Once complete, the survey will cover 20 square degrees in four fields to a depth of ~1 uJy rms/beam at 1.2 GHz, providing a unique combination of depth and breath. Crucially, the MIGHTEE fields have excellent multi-wavelength coverage, enabling a full census of galaxy properties. I will provide an overview of the early-science results from the radio continuum part of the survey, focussing on the role radio-loud AGN play in galaxy evolution.

27 Jan
Filaments: fantastic beasts and where to find them
Alvaro Hacar (University of Vienna)
3.45pm  TEAMS

Modern astronomical studies have identified filaments at all scales, from cosmological Mpc-like sizes down to the small sub-pc features prior the formation of individual stars. The presence of these ubiquitous filamentary structures reveals the intrinsic multiscale and anisotropic nature of the physical mechanisms governing our Universe. However, the internal properties of these filaments dramatically change depending on their scale, environment, and origin. During my talk I will introduce a local (parsec-like) perspective on the study of filaments and star formation in our own Galaxy. I will discuss the formation, stability, and evolutionary properties of filamentary gas structures as well as some of the techniques used for their identification and analysis. Moreover, I will introduce some of the later results and challenges on the study of Milky Way filaments using state-of-the-art radiotelescopes such as ALMA. By discussing their similarities and differences, as well as the alternative approaches used for their study, my aim is to establish a direct dialogue between researchers working on filaments at different scales, from Cosmology to Galactic works.

03 Feb
Probing black hole-galaxy co-evolution from de-biased scaling relations
Francesco Shankar (Southampton)
3.45pm  TEAMS

It has been claimed for decades that almost all galaxies in the local Universe host at their centre a supermassive black hole (SMBH) the mass of which appears to be tightly correlated with the stellar mass and the random motion ("velocity dispersion", sigma) of the stars in the host galaxy. In this talk I will first review the state of the art in this field. I will then highlight that significant biases affect local black hole-galaxy correlations. I will specifically show that the majority of quiescent early-type galaxies with central black hole dynamical mass estimates have significantly higher velocity dispersions than local typical galaxies of similar stellar mass. Through aimed Monte Carlo simulations, residual analysis, and the comparison with latest AGN clustering measurements, I will then illustrate that present data sets of active and quiescent galaxies strongly favour on average lower SMBH masses than previously thought, and point to velocity dispersion as more fundamental'' than galaxy stellar mass, galaxy size or Sérsic index. I will then move on discussing the main implications of these findings, in particular: 1) The implied black hole radiative efficiencies and obscured fractions; 2) the consequences on feedback from active black holes and SMBH binary gravitational waves; 3) the connection to cosmological models that rely on velocity dispersion, rather than stellar mass, as main driver of black hole growth.

17 Feb
Cosmic Concordance or Tension: Cosmology from the Kilo-Degree Survey
Catherine Heymans (University of Edinburgh)
3.45pm  Zoom

The Planck space mission has released exquisite observations of the early universe, providing the strongest evidence yet that the universe we live in is very dark indeed. Its precise results show that our universe is composed of 27% dark matter and 68% dark energy, while less than 5% is made up of the baryonic material that we are familiar with on Earth. With their long-standing quest to make these precision measurements essentially now concluded, cosmologists are rapidly turning their attention to a much bigger and further-reaching question: what is the exact nature of this dark universe? I will introduce the Kilo-Degree Survey (KiDS), which we’ve used to map out the invisible dark matter and confront theories on the origins of dark energy. Interestingly the increasing precision that KiDS has recently reported reveals a tension with Planck’s initial conclusions. Is this is a sign that new data challenges lie ahead, or is it our first hint that the universe is truely exotic and that in order to understand the dark universe we will need some new physics that will forever change our cosmic view.

24 Feb
The travelling telescope
Susan Murabana (Travelling Telescope)
3.45pm  TEAMS

The telescope has been around for more than 400 years and yet most people have never had the chance to look through one. We take our portable computerised telescope to schools and villages and provide guided tours of the night skies to school kids, tourists and members of the public. We also take our 8 meter mobile planetarium around and have recently completed our bamboo dome in the heart of Nairobi. Our talk will focus on this journey and our future plans.

03 Mar
Star forming emission line galaxies at z~1 as cosmological tracers
Violeta Gonzalez-Perez (CIAFF, Universidad Autónoma de Madrid)
3.45pm  TEAMS

Current and future cosmological surveys (SDSS-IV/eBOSS, DESI, Euclid) are targeting star forming galaxies emission line galaxies at z~1. These galaxies are dominated by [OII] emitters when the selection is done using optical instruments. This talk will start with an overview of the different techniques to study the formation and evolution of galaxies computationally to then focus on the modelling of star forming emission line galaxies (ELGs). Using a state-of-the-art model of galaxy formation and evolution we explore the global properties of [OII] emitters, including their large scale environment. Model galaxies are selected with cuts in different properties such that the samples can be directly compared with a range of both narrow and wide observational surveys: DEEP2, VVDS, eBOSS and DESI. The selected [OII] emitters are hosted by haloes with halo masses above 10^10.3 Msun/h, with ~90% of them being central star-forming galaxies. The predicted mean halo occupation distributions of [OII] emitters has a shape typical of that inferred for star-forming galaxies, with the contribution from central galaxies being far from the canonical step function. The mean halo occupation distribution for central [OII] emitters can be described as the sum of an asymmetric Gaussian for disks and a step function for spheroids, which plateaus below unity. The large scale environment of model galaxies is obtained for fixed number density samples, using a velocity-shear-tensor and a tidal-tensor algorithms. About half of the fixed number density ELGs live in filaments, following the distribution of SFR selected galaxies with the same number density, and a third in cosmic sheets. SFR cut selected ELGs and general galaxies with equal number density, have the same large scale bias but their clustering below separations of 1Mpc/h are different. Although as a first approximation the samples that will be targeted by DESI, 4MOST, MSE, etc. are simply star forming galaxies, the model ELGs do trace a slightly different large scale environment.

10 Mar
The star formation histories of massive quiescent galaxies
Adam Carnell (University of Edinburgh)
3.45pm  TEAMS

The star formation histories of galaxies have the potential to provide strong constraints on the most important processes driving galaxy evolution and quenching. However, obtaining reliable measurements from observational data is fraught with difficulties. In this talk I will introduce Bagpipes, a new public Python code that allows users to build sophisticated model galaxy spectra and fit these to combinations of spectroscopic and photometric observational data using cutting edge Bayesian statistical techniques. I will demonstrate the use of this method to analyse a sample of ultra-deep spectra for massive quiescent galaxies at 1.0 < z < 1.3 from VANDELS, investigating quenching physics at high redshift by constraining the SFHs of these objects and the stellar mass vs stellar age relationship. Finally I will discuss ongoing efforts to identify the first massive quiescent galaxies at z > 3, and what these objects can tell us about massive galaxy formation during the first billion years.

17 Mar
SuperWASP Variable Stars: Classifying Stars Using Citizen Science
Heidi Thiemann (Open University)
3.45pm  TEAMS

SuperWASP, the world's leading ground-based survey for transiting exoplanets, used wide-field robotic telescopes to continuously image the night sky for a decade. As well as detecting ~200 exoplanets, SuperWASP also built up an archive of observations of >30 million bright stars, ideal for studies of stellar variability. This includes stars displaying pulsations or outbursts, as well as eclipsing binary stars and stars displaying rotational modulation. A recent period-search of this archive identified ~1.6 million possible periods in ~750,000 objects, each of which was converted to a light curve. To classify each light curve, we’ve enlisted the help of citizen scientist volunteers in a project called SuperWASP Variable Stars, hosted on the Zooniverse platform. We’re combining the ‘wisdom of the crowd’ with machine learning to classify all ~1.6 million light curves and find unique stellar variables. So far, over 300 new variables have been identified, including extreme stellar binaries. In this talk, I will highlight some of the most exciting results of the project so far, and describe the next steps for the SuperWASP Variable Stars team.

24 Mar
The causes of the red sequence and the green valley: a new galaxy paradigm revealed by Herschel
Stephen Eales (Cardiff)
3.45pm  TEAMS

In the first two thirds of the seminar, I will show how the Herschel Space Observatory has given us a radically different perspective on the galaxy population from the traditional optical view. I will argue that the paradigm that galaxies fall in two distinct classes, with some catastrophic 'quenching process' moving a galaxy from one class into another, is wrong. In this part of the seminar, I will also touch on the use of the lensed systems found in the Herschel surveys to investigate galaxy formation. In the last third of the seminar, I will describe a new project we have started to survey the Andromeda Galaxy at submm wavelengths.

21 Apr
The MIGHT(EE) of MeerKAT: Giant radio galaxies may be far more common than we thought!
Jacinta Delhaize (University of Cape Town)
3.45pm  TEAMS

I will summarise the results of our recent paper (Delhaize et al., 2021) on the discovery of two giant radio galaxies (GRGs) in the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey. GRGs are the largest single objects in the Universe and are relatively rare, with fewer than 850 currently known. Only around 7% of these have sizes greater than 2Mpc, yet we have detected two such objects within a 1 square degree field in MIGHTEE-COSMOS Early Science observations. Only the cores of these GRGs were clearly visible in previous high resolution observations with the VLA. However, the unprecedented surface brightness sensitivity of the new MeerKAT telescope allowed the diffuse emission of the large-scale jets and lobes to be detected for the first time. We calculate a very small probability of finding two or more such GRGs in the field, supporting the hypothesis that the sky density of GRGs is likely much higher than previously thought. This could have important ramifications on our understanding of the AGN duty cycle and the impact of the radio jets in the evolution of the host galaxy. The two GRGs presented here may be the first of a new population to be revealed through surveys like MIGHTEE, which provide exquisite sensitivity to diffuse, extended emission.

28 Apr
Gas and star formation in the nearby universe with the ALMA-MaNGA QUEnching and STar formation (ALMaQUEST) survey.
Sara Ellison (University of Victoria)
3.45pm  TEAMS

Understanding the processes that regulate star formation in galaxies remains at the heart of modern extra-galactic astronomy, and debate continues as to why some galaxies exhibit powerful starbursts whilst others are largely dormant. The key to progress in this arena lies with assembling large, diverse samples of galaxies for which we can measure all of the critical ingredients, such as the current star formation rate (SFR) and gas content. However, it is insufficient to simply measure global galactic quantities, as we know that a given galaxy will manifest considerable internal diversity in its star formation activity. It is therefore essential to study gas and star formation on spatially resolved scales. The ALMA-MaNGA QUEnching and STar formation (ALMaQUEST) survey combines maps of stellar properties obtained from the MaNGA (optical) integral field unit survey with ALMA CO (1-0) maps on a common kpc-scale grid, in order to tackle questions of star formation in local galaxies. The 46 galaxies in the ALMaQUEST sample span a wide range of SFRs, including both normal star forming galaxies, as well as those both on their way to quenching, and those undergoing starbursts. In this talk, I will present the ALMaQUEST view of understanding the interplay of gas and star formation across this broad galactic landscape.

05 May
Evolution of global metallicities & radial metallicity profiles in disc galaxies: Insights from L-GALAXIES 2020 and MaNGA
Rob Yates (University of Surrey)
3.45pm  TEAMS

Global and sub-galactic metallicities provide a key insight into constraining galaxy evolution. In this talk, I will present recent results on the evolution of global and sub-galactic metallicities as revealed by MaNGA and the new L-GALAXIES 2020 semi-analytic model of galaxy evolution (https://ui.adsabs.harvard.edu/abs/2021MNRAS.503.4474Y/abstract). Very efficient direct metal enrichment of the circumgalactic medium by SNe is required in L-GALAXIES 2020 in order to match the gas (Zg) and stellar (Zs) metallicity profiles seen in a sample of 571 MANGA disc galaxies. These more metal-rich outflows do not require increased mass-loading factors, in contrast to some other galaxy evolution models. Importantly, this new L-GALAXIES 2020 model is also able to simultaneously reproduce the observed global mass – metallicity relations for gas and stars at z = 0, their evolution back to z ∼ 2−3, and the metal abundances observed in the intracluster medium, as well as other key galaxy scaling relations. Finally, I will show that massive disc galaxies in L-GALAXIES 2020 have slightly flatter Zg profiles than their lower-mass counterparts, due to more efficient enrichment of their outskirts via inside-out growth and metal-rich accretion. Such a weak, positive correlation between stellar mass and Zg gradient is also seen in MaNGA and MUSE, although below log10(Ms/Msun) ∼ 10.0 this is strongly dependent on the metallicity diagnostic and morphological selection.

12 May
Unveiling HI Reionization: Status and the Constraining Power of High-z QSO Absorption Features
Jose Oñorbe (University of Seville)
3.45pm  TEAMS

How and when the first luminous sources reionized diffuse baryons in the intergalactic medium (IGM) is one of the most fundamental open questions in cosmology. I will first present a summary on our present knowledge on this process and the most promising observational techniques currently used to further investigate it. I will show that even after reionization is complete, its thermal vestiges persist in the IGM to much later times. Therefore, by measuring the thermal state of the IGM from the statistics of the high-z (z~5-6) Lyman-alpha forest, we can place constraints on reionization. I will present results from hydrodynamical simulations that make use of a new method to generate self-consistent inhomogeneous thermal and reionization histories and direct constraints on when HI reionization happened and how much energy per atom was injected into the IGM. Finally, I will show that at even higher redshifts when the Lyalpha forest line saturates it can be possible to use the "metal line forest" to provide constraints on the global neutral hydrogen fraction and metallicity abundance.

19 May
A cloud-scale view of the star formation process
Eva Schinnerer (Max-Planck Institute)
3.45pm  TEAMS

Where do stars form and how is their formation regulated across galactic disks are two critical questions for our understanding of the star formation process. High angular observations of nearby galaxies allow us to sample the star formation process across entire galactic disks reaching now regularly the scales of the star-forming units, namely Giant Molecular Clouds (GMCs) and HII regions. Such data provide new insights on the molecular gas reservoir and its role in the star formation process as well as information on the importance of galactic components such as bulges, stellar bars, spiral arms and active galactic nuclei (AGN) in the conversion of cold (molecular) gas into stars. I will introduce the PHANGS (Physics at High Angular resolution in Nearby GalaxieS) survey and present a few highlights from the ongoing research of the collaboration.

02 Jun
A multi-wavelength study of star formation and nuclear activity in submillimetre galaxies
Jo Ramaswamy (UK Astronomy Technology Centre)
3.45pm  TEAMS

I will present an overview of my PhD research into star formation in galaxies at high redshift. The SCUBA-2 Cosmology Legacy Survey is a rich dataset, unique in its depth and sky coverage at submillimetre wavelengths and covering a range of well-studied extragalactic survey fields. I have used it as the starting point for three projects looking at the nature of submillimetre galaxies, investigating the following questions: What is the relationship between supermassive black hole growth and star formation in massive galaxies? How do the low-frequency radio properties of star-forming galaxies compare with their submillimetre properties, and what might we infer from their radio spectra? And can cosmological simulations accurately reproduce the observational properties of highly star-forming galaxies? I will discuss my work on these topics, as well as introduce the project that I am now working on at the UK Astronomy Technology Centre, AtLAST - a three year design study making the case for a 50m submillimetre telescope to be built in the 2030s.

09 Jun
Caught in the act: using post-starburst galaxies to chart galaxy transformation over cosmic time
Kate Rowlands (STSI)
3.45pm  TEAMS

One key problem in astrophysics is understanding how and why galaxies stop forming stars. The exact mechanisms that lead to the disruption of the gas supply, the relative importance of different quenching mechanisms, and the timescales involved are still poorly understood. Post-starburst galaxies are an ideal laboratory to study the galaxy transition process as they have undergone a recent, rapid shutdown in star formation. My recent work showed that post-starburst galaxies are not completely devoid of gas, which challenges the rapid quenching mode thought to form the quiescent population. Using wide-area photometric and spectroscopic surveys, I will describe what the stellar, gas, and dust properties of post-starburst galaxies reveal about the processes causing galaxies to transition from star forming to quiescent.

16 Jun
Chasing Neutral Hydrogen: an Intensity Mapping view of the large scale structure
Marta Spinelli (Astronomical Observatory of Trieste)
3.45pm  TEAMS

Radio telescopes such as MeerKAT, and in the future SKA, can map the spatial distribution of the low redshift cosmic neutral hydrogen using Intensity Mapping techniques for the 21 cm line. These measurements can unveil the underlying large-scale structure of the Universe and contribute in a fundamental way to constrain cosmological parameters. A key challenge is the subtraction of the bright foregrounds, orders of magnitude stronger than the 21cm signal. It is, therefore, crucial to assess through simulations the performance of foreground cleaning in realistic scenarios, improving both the sky model and the instrument characterization. In this talk, I will present the current status of an Intensity Mapping survey with MeerKAT in single-dish mode. I will also discuss the effort, carried out with the SKA Intensity Mapping Focus Group to construct a realistic mock data cube for both MeeKAT and the SKA, and to test and compare different foreground cleaning methods.

11 Sep
Extragalactic Star Clusters and the Assembly History of Galaxies
Jean Brodie (UCSC)
3.45pm  C12

02 Oct
Title TBC
CANCELLED
3.45pm  C12

09 Oct
Kinematics features of the Milky Way globular clusters
Andrés Piatti (Astronomical Observatory of Cordoba)
3.45pm  C12

We report results on the kinematics of Milky Way globular clusters based on updated space velocities for nearly the entire globular cluster population. We found that a 3D space with the semi-major axis, the eccentricity and the inclination of the orbit with respect to the Milky Way plane as its axes is helpful in order to dig into the formation of the globular cluster system. We find that globular clusters formed in-situ show a clear correlation between their eccentricities and their orbital inclination in the sense that clusters with large eccentricities also have large inclinations. Accreted globular clusters do not exhibit a relationship between eccentricity and inclination, but span a wide variety of inclinations at eccentricities larger than 0.5. These findings can be interpreted as if globular clusters formed from gas that collapsed radially in the outskirts, with preference for relative high infall angles. As the material reached the rotating forming disc, it became more circular and moved with lower inclination relative to the disc. A half of the globular cluster population was accreted and deposited in orbits covering the entire range of energies from the outer halo to the bulge.

16 Oct
Extra-galactic archaeology - studying galaxy formation from their metallicity and elemental abundance distributions
Chiaki Kobayashi (Hertfordshire)
3.45pm  C12

Stars are fossils that retain the history of their host galaxies. At the end of their lives, some explode as supernovae, producing heavy elements that are distributed into the surrounding interstellar gas. New stars that are created from this gas contain the elements that were produced from the previous generations of stars. From the spatial distribution of elements, it is therefore possible to constrain the star formation and chemical enrichment histories of the galaxies. This approach, Galactic Archaeology, has been popularly used for our Milky Way Galaxy. It can also be applied to external galaxies thanks to the recent and future observations with integral field units such as MaNGA and JWST/NIRSpec. My team has been running hydrodynamical simulations from cosmological simulations including detailed chemical enrichment. I will show how well our model reproduces the elemental abundances in the Milky Way, and how the radial distribution of elements depends on the merging history of galaxies and on their environment. I will then propose a new way to constrain the formation timescale of disk galaxies from their CNO abundances for the era of JWST.

23 Oct
Molecular gas flows driven by radio jet activity in massive galaxies
Helen Russell (Nottingham)
3.45pm  C5

Gas accretion onto a supermassive black hole can launch powerful, high-velocity winds and relativistic jets into the host galaxy. Recent discoveries of massive, kpc-scale gas flows show that these winds and jets plough into the surrounding interstellar medium and disrupt and expel cold gas clouds, which would otherwise collapse to form stars. Known as AGN feedback, this is thought to be the essential mechanism slowing massive galaxy growth at late times in the Universe. With the arrival of the Atacama Large Millimeter Array (ALMA), we can now resolve the structure of these cold gas flows to understand how the supermassive black hole's energy is coupled to the host galaxy. I will review observations of a dozen early ALMA targets, which reveal a distribution of morphologies from filamentary to disk-dominated structures. In most systems, half to nearly all of the molecular gas lies in filamentary gas flows which are entrained around radio bubbles inflated by the jet. Uplifted gas will stall and fall back to the galaxy in a circulating flow, which may eventually fuel the black hole. The distribution in morphologies therefore implies slowly evolving molecular structures driven by the episodic activity of the central black hole.

06 Nov
Are galactic star formation and quenching governed by local, global, or environmental phenomena?
Asa Bluck (Cambridge)
3.45pm  C12

20 Nov
The structure of galactic thick disks
Marie Martig (LJMU)
3.45pm  C12

04 Dec
Star formation in spiral arms
Clare Dobbs (Exeter)
3.45pm  C12

I will present ongoing work investigating the formation of molecular clouds and stellar clusters from galaxy scales to individual clouds. I will first highlight main presults from previous simulations of spiral galaxies which show the formation of giant molecular clouds via self-gravity and cloud-cloud collisions. In these simulations, stellar feedback is found to be important both to limit the star formation rate, and determine the properties of the clouds. I will also show results from recent models of the galaxy M33, which are able to reproduce the observed properties of molecular clouds in that galaxy. I will then move on to smaller scale simulations which are better able to resolve stellar feedback, including ionisation, and stellar clusters. We study the effects of photoionsation and find that unlike isolated cloud type simulations, ionisation fronts traverse from star forming clouds to other material. The ionisation is able to compress this material into denser filaments and clouds, triggering star formation. After an initial stage of triggered star formation, the star formation rate is then reduced compared to the case without any stellar feedback. The ionisation also produces less gravitationally bound clusters compared to without ionisation. Finally I will present some results from simulations of colliding clouds, showing the formation of young massive clusters (YMCs), and highlighting the conditions under which YMCs can be expected to form.

11 Dec
A MUSE study of nuclear star clusters in dwarf galaxies
Evelyn Johnston (Pontifica Universidad Catolica de Chile)
3.45pm  C12

Nuclear star clusters (NSCs) are a common characteristic of dwarf galaxies, particularly higher-mass dwarfs. There are two main scenarios discussed in the literature to explain their formation, in-situ formation and migration, and clues to the formation of an NSC lie in its SFH. However, NSC spectra are contaminated by light of the host galaxy, making it difficult to isolate the stellar populations of the NSC itself. As part of the Next Generation Fornax Survey (NGFS), I am using BUDDI (Bulge-Disc Decomposition of IFU data) to overcome this issue. BUDDI uses information from the entire datacube to create a wavelength-dependent model of each each component within a galaxy, from which one can extract a spectrum representing purely the light from that component.

22 Jan
Chondritic Meteorites and the and the Chronology of the Nascent Solar System
Tim Gregory (British Geological Survey)
3.45pm  C12

Chondrites are shrapnel from unmolten planetesimals that arrived on the Earth, intact, after an interplanetary journey from the Asteroid Belt. Often thought of as cosmic sediments, chondrites are made from the dust from which the asteroids, comets, and planets formed, and therefore preserve material from the onset of the Solar System’s rock record. They hold information about when, and how, our Solar System formed. A key constraint on models of Solar System formation is the timing, order, and duration of events in the protoplanetary disc. The two cornerstones of early Solar System chronology — the extinct 26Al→26Mg and the extant 238,235U→206,207Pb chronometers — are powerful tools, but often yield conflicting results. Understanding and resolving these conflicts is key to our understanding of how the first solids formed, and how the Solar System evolved from a disc of gas orbiting a protostar to the clockwork system of planets we see today.

05 Feb
WISDOM: Probing Supermassive Black Holes and their Immediate Environments with ALMA
Martin Bureau (Oxford)
3.45pm  C12

I will present key results from the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM), a high resolution survey of molecular gas in galaxy nuclei. First, I will show that CO can be used to easily and accurately measure the masses of the supermassive black holes lurking at galaxy centres. I will then discuss substantial ongoing efforts to do this, and present many spectacular new ALMA measurements, the latest of which rival the best black hole measurements to date. This opens the way to literally hundreds of measurements across the Hubble sequence (in both active and non-active galaxies) with a unique method. I will also briefly show how the same data allow to study the spatially-resolved properties of the giant molecular clouds in nearly all the galaxies studied. This will yield cloud censuses in non-local galaxies (including early-type galaxies) for the first time, providing a new tool to understand and contrast the star formation efficiency across galaxies. Already, it appears that basic cloud properties are not universal and vary systematically along the Hubble sequence, contrary to long-held assumptions.

19 Feb
From elite sport to social good applications, a combined use of geospatial sciences and machine learning
Bertrand Perat (Nottingham)
3.45pm  C12

With a background in Geospatial Sciences and a recent move towards data analytics and machine learning, my research interests lie somewhere in between these two worlds. After introducing some of the main Geospatial research domains, I will take you through some facets of my PhD, centered around the use of Global Navigation Satellite Systems in the quest for Olympic Gold. I will then cover a number of projects relying on the use of Satellite Imagery and machine learning to automate various tasks from land use mapping, to road quality estimation in developing countries. The final focus will be on vulnerability mapping in Asia, through the automated and large-scale detection of kilns used in brickmaking, an industry largely uncontrolled but suspected to be linked to modern slavery. Finally, I will detail what this domain can learn from other fields, including Astronomy.

04 Mar
Halo and galaxy formation in the cosmic web
Marius Cantun (Durham/Leiden)
3.45pm  C12

I will discuss a few key advancements in our understanding of the cosmic web and its effect on the properties of collapsed objects, such as dark matter haloes and galaxies. The cosmic web represents the intricate pattern seen in the distribution of matter and galaxies in the cosmos. It consists of large nearly-empty voids, separated by tenuous sheets that connect to form prominent filamentary bridges, which, in turn, shape the accretion into galactic- to cluster-mass systems. Similar to halos and galaxies, the web environments come in a diversity of shapes and sizes: from prominent filaments connecting galaxy clusters to tenuous tendrils crisscrossing the cosmic voids. This diversity is easily seen in cosmological simulations, and, recently, with the advent of deep galaxy surveys (e.g. GAMA, upcoming DESI BGS) also in observations. The properties of haloes and galaxies are correlated to their web environment, but to a lesser extent than initially thought. While the mass function of haloes and galaxies varies strongly between web environments, at fixed mass the correlations with the cosmic web are more subtle, as I shall discuss. Some examples include the alignment of halo and galaxy spins with their host filament, and the propensity of galaxies to be redder when closer to filaments. Part of the challenges in describing these correlations come from the fact that filaments have a large diversity and that galaxy properties are sensitive to the nature of their filaments. Future improvements would mean going beyond the simple classification into knots, filaments, and sheets, which, while easy to describe and imagine, contains only a limited amount of physical information

18 Mar
CANCELLED: Star forming emission line galaxies at z~1 as cosmological tracers
Violeta Gonzalez-Perez (LJMU)
3.45pm  C12

01 Apr
MS Teams video: Unveiling the inner structures of AGN from multi-waveband reverberation mapping
Ian McHardy (Southampton)
3.45pm  C12

06 May
Linking insights into the disc, bulge and halo for a holistic approach to constraining the assembly of the Milky Way
Ted MacKerth (Birmingham)
3.45pm  C12

13 May
Linking dynamics and stellar populations with 3D spectra
Jesus Falcon Barroso (Instituto Astrofisica de Canaries)
3.45pm  C12

20 May
Chandra’s Impact on Extragalactic Astrophysics
Belinda Wilkes (Smithsonian Astrophysical Observatory)
3.45pm  C12

NASA's Chandra X-ray Observatory was launched on 23 July 1999 by the Space Shuttle Columbia. Now celebrating its 20th year of operations, Chandra continues to be an indispensible tool for expanding the frontiers of knowledge throughout astrophysics. Chandra's uniquely high (sub-arcsec) spatial, and spectral resolution have facilitated the deepest (7Ms) image of the X-ray sky, finding it to be dominated by active galaxies, and the highest quality X-ray spectra to date, revealing the dynamic, multi-component structure of material close to the SMBH. I will provide a review of Chandra and its broad scientific impact, before concentrating on Chandra's results on extragalactic science including galaxies, clusters of galaxies, active galaxies and cosmology.

27 May
How high density environments shape the evolution of galaxies over cosmic time
Remco van der Burg (ESO)
3.45pm  C12

03 Jun
Active Galactic Nuclei in an ocean of data
Sotria Fotopoulou (Bristol)
3.45pm  C12

Active galactic nuclei (AGN) are signposts of the luminous growth of supermassive black holes. During this phase, strong winds can impact the formation of new stars in a galaxy. The short lifetime of the AGN phase makes them very rare objects. Moreover, they are often found with varying methods across the electromagnetic spectrum, with very little overlap between the selected galaxy samples. In tandem with the traditional geometrical paradigm that gives rise to the AGN types (obscured versus unobscured), pieces of evidence point towards an evolutionary approach  linking the various AGN populations and also the host galaxy. Upcoming surveys such as Euclid and LSST will offer a significant boost in galaxy and AGN studies due to the unparalleled sample size of billions of detections. Machine-learning techniques are arguably a very efficient approach to selecting AGN,  next to traditional AGN selection methods. Such methods can be trained to identify known classes of objects, but they can also be used for novelty and anomaly detection. I will present recent results and future prospects of machine-learning AGN identification methods in anticipation of Euclid.

10 Jun
POSTPONED until 17th #shutdownSTEM – Halo and galaxy formation in the cosmic web
Marius Cantun (Leiden)
3.45pm  C12

17 Jun
Halo and galaxy formation in the cosmic web
Marius Cantun (Leiden)
3.45pm  C12

03 Oct
Learning about cosmology from non-linear structure formation
Julian Merten (Bologna & Oxford)
3.45pm  C12

The standard model of cosmology is very successful in describing many key observations with only very few parameters and at high significance. However, this phenomenological description of the Universe is no real attempt to understand the true nature of its most dominant components today, dark matter and dark energy. More importantly, tension between theoretical predictions and observations arises when entering the astrophysical realm of dark matter haloes that decoupled from the Hubble flow. The observed mass function of galaxy clusters, the observed density profiles and substructure contents of objects spanning all mass ranges are not quite in line with theoretical predictions. This is why we are most interested in the non-linear regime of structure formation. While for many on-going and planned cosmological surveys this regime is a mere nuisance which needs to be controlled in order to obtain unbiased cosmological parameters, its detailed study is also one of the most promising ways to achieve deeper insight into the mechanisms of structure formation.  In my presentation I will show how we can use gravitational lensing to unveil and study non-linear structure in the sky. I will present novel mass mapping techniques which combine many different probes into a joint reconstruction of the density field. In order to optimally characterise such maps beyond the usual approach of 2-point statistics and 1D parametric density profiles, we deploy a number of machine learning techniques from the field of computer vision, which allow tighter inference on the most degenerate cosmological models. All these techniques are based on the use of modern many-core computational architectures (such as GPUs), which I will also introduce, and which are able to harvest upcoming large data sets efficiently. I will present results from earlier lensing surveys such as CLASH and show our current efforts within the on-going KiDS survey. I will end my presentation with our plans to fully exploit the potential of the upcoming Euclid satellite.

Host:  James

10 Oct
Misaligned black hole accretion discs
Bec Nealon (Leicester)
3.45pm  C12

Accretion discs around rotating black holes are often assumed to be aligned with the black hole spin. Relaxing this assumption by inclining the disc means that the rotation of the black hole is able to affect the disc evolution, leading to previously unexplored structures in the disc. I will present three-dimensional simulations investigating the evolution of such tilted discs at a range of inclinations. In the small inclination case we identify an oscillatory disc profile, in agreement with previous analytical predictions. In the high inclination case we confirm disc breaking and tearing, where the disc is torn in independently precessing rings of gas. I will then consider applications of these structures to observational features, considering the currently unexplained phenomenon of quasi-periodic oscillations. Turning to geometrically thick accretion flows we consider a torus (with a donut shaped profile), such as would form from a tidal disruption event. Simulating a torus in three-dimensions is difficult as they may be unstable to the non-axisymmetric hydrodynamic Papaloizou-Pringle instability. I will present our simulations of an idealised, circularised torus that has similar parameters to a previously simulated tidal disruption remnant and show that i) it is unstable to this instability and ii) this instability is capable of driving angular momentum transfer. Our simulations imply that the initial accretion rate (and hence lightcurve) of tidal disruption events may be constrained by this instability rather than the magneto-rotational instability in the case of extremely weak initial magnetic fields.

Host:  Charutha

17 Oct
Astro-ecology: saving endangered animals from outer space
Claire Burke (LJMU)
3.45pm  C12

Species of animals are disappearing from Earth at a rate not seen since the extinction of the dinosaurs. Protecting biodiversity is vital for a multitude of environmental and societal reasons. To form effective conservation strategy detailed understanding of wildlife populations is needed. However ecosystem knowledge is still commonly based on data gathered through foot surveys. Drones offer a major advantage for ecosystem surveying, animal tracking and monitoring for poachers as they can survey large areas or difficult terrain quickly with minimal disturbance to wildlife. But this comes with its own challenges, such as optimizing observing strategy and analysing the ever increasing quantity of data produced. In a world first collaboration between astronomers and ecologists, we are adapting techniques used in astrophysics to help revolutionise conservation ecology through the use of thermal equipped drones. I will discuss the solutions we are developing and some of our recent successes.

Host:  Martha

24 Oct
Satellite galaxies in groups and clusters: A novel Semi-Empirical Model
Pip Grylls (Southampton)
3.45pm  C12

I present STEEL our new STatistical sEmi-Empirical modeL designed to probe the distributions of satellite galaxies in groups and clusters over many epochs. An accurate picture of halo richness over a large redshift range is crucial to our understanding of how hierarchal assembly effects galaxy population statistics. I show how by discarding traditional merger trees in favour of number density functions I am able to resolve ‘rare’ structures simultaneously with the general subhalo population at all redshifts. I show that using only dark matter structure, dynamical friction, and abundance matching a good match to the satellite population can be found over many epochs. Finally I will discuss how using the statistical framework we can test statistics of galaxy populations and galaxy formation models.

Host:  Sunny

26 Oct
Properties of the diffuse baryons in Galaxy Clusters out to the virial radius
Stefano Ettori (Osservatorio Astronomico di Bologna)
3 pm  C12 *Note: Special time 3-4pm

Galaxy clusters are dark-matter dominated systems enclosed in a volume that is a high-density microcosm of the rest of the universe. They are the nodes of the Cosmic Web, constantly growing through accretion of matter along filaments and via occasional mergers. With most of the baryons in the form of X-ray emitting plasma, clusters are thus excellent laboratories for probing the physics of the gravitational collapse of dark matter and baryons, for studying the non-gravitational physics that affects their baryonic component, and as cosmological probes. I will revise the present constraints we have on the ICM in the regions approaching the virial radius from our ongoing X-COP project, what are the open questions on the properties of the ICM there, and how we can try to characterize it with our next XMM-Newton Heritage Cluster Project and with the future generation of X-ray (Athena) and radio (SKA) telescopes.

Host:  Jake

07 Nov
The Emergence of Structure during the Epoch of Reionization
Martin Haehnelt (Cambridge)
3.45pm  C12

I will give an overview of recent constraints on reionization from Lyman-alpha and 21cm emission/absorption with special emphasis on the implications of the rather large scales (>=50cMpc) of observed large Lyman-alpha opacity fluctuations at z>~5.5 on the timing of reionization and the nature of ionizing sources.

Host:  Joel

14 Nov
Asymmetric drift in galaxies: trends and applications
Kyle Westfall (UCO Lick Observatory)
3.45pm  C12

Asymmetric drift is the rotational lag of the stellar component of a galaxy disk with respect to the circular speed defined by its gravitational potential.  The underlying physical mechanism is that gas efficiently dissipates energy allowing it to settle into circular orbits, whereas the collisionless stars maintain a velocity ellipsoid that acts as an effective dynamical pressure.  It is this direct link to the galactic potential and the stellar phase-space distribution function that makes asymmetric drift a powerful tool in quantifying the dynamical state of galaxy disks.  I will present two ongoing works.  The first uses data from the DiskMass survey to measure the axial ratios of the stellar velocity ellipsoid, for which asymmetric drift is a key aspect of the measurement.  The second uses data from the recent MaNGA survey in a more general study of asymmetric drift in ~800 galaxies across the color-magnitude diagram.  Finally, I will discuss how our approach and these results could be used to extend the primary scientific goal of the DiskMass survey --- to provide robust, dynamical measurements of the baryonic masses of galaxy disks --- to new regimes.

Host:  Tom

21 Nov
Observing the multi-scale cosmic web at high redshift and quantifying its impact on galaxies
Clotilde Laigle (Oxford)
3.45pm  C12

The cosmic web is the large-scale metric in which galaxies form and evolve. Recent measurements from low-redshift spectroscopic surveys support a picture in which the large-scale environment impacts both the dynamics and the assembly history of galaxies. However extracting the cosmic web from observed datasets is still a challenge, in particular at high redshift where large and complete spectroscopic surveys are extremely costly. At these redshifts, though, we expect a stronger dependency of galaxy properties on the geometry of the accretion, which makes this extraction pivotal to understand galaxy evolution. I will give an overview of the current status of cosmic web analysis from high redshift observations, either photometric data or lyman-alpha forest surveys. While relying on a pilot study in COSMOS, I will present results about the co-evolution of galaxies and the cosmic web at high redshift and I will show how this study can be extended with future probes including LSST, Euclid, PFS and MOSAIC on the ELT.

Host:  Rachel

26 Nov
Gas stripping and star formation in galaxies as a function of their environment
Bianca Poggianti (INAF)
3.45pm  A113

To understand galaxy evolution it is essential to know how and why the gas content of galaxies evolves. There are several physical processes that can affect a galaxy gas reservoir, and in galaxy clusters ram pressure stripping is considered the most efficient such mechanism. I will show how integral field spectroscopy can be used to study the removal of gas from galaxies in clusters and groups, focusing on the consequences that such removal has for the AGN activity and for the star formation activity in the disks and in the tails of stripped gas.

Host:  Lizzie

05 Dec
Galaxy evolution since cosmic noon: lessons from gas, dust and star formation
Stijn Wuyts (Bath)
3.45pm  C12

Integral-field spectroscopic surveys such as MaNGA in the nearby Universe and KMOS3D out to z~2.6 are providing us with a 3D mapping of the ionized gas emission in large samples of mass-selected star-forming galaxies. Their dynamics reveal the depth of gravitational potentials in which the gas orbits. Broad components to the line emission shed light on galactic-scale outflows driven by star formation and active nuclei. Moreover, the spatial distribution of ionized gas emission serves as a tracer of where within galaxies the (unobscured) star formation is taking place. Complementing these rest-optical observations are far-infrared measures of dust and CO line emission, probing the cold gas reservoirs, molecular outflows and the distribution of dust-obscured star formation. I will present recent findings on the nature and evolution of star-forming galaxies from cosmic noon to the present day, obtained by combining multi-wavelength tracers of dust and star formation, ionised and molecular gas.

Host:  Amy

12 Dec
Galaxy evolution in the metric of the cosmic web
Katarina Kraljic (Edinburgh)
3.45pm  C12

The strikingly anisotropic large-scale distribution of matter, the so-called cosmic web, is made of an extended network of voids delimited by sheets, themselves segmented by high-density filaments, within which matter flows towards compact nodes where they intersect. Do the properties of galaxies, such as e.g. their morphology, retain a memory of these large-scale cosmic flows from which they emerge? And what are the signatures of this environment at different locations within the cosmic web? In this talk, I will address these questions using the set of observed and virtual galaxies, from the spectroscopic survey GAMA and large-scale hydrodynamical simulation HORIZON-AGN, respectively. I will argue that on top of stellar mass and large-scale density, the traceless component of the tides from the anisotropic large-scale environment also shapes galactic properties. I will show that these results can be qualitatively explained in terms of anisotropic assembly bias by an extension of excursion theory.

Host:  Alex

16 Jan
Deep imaging - using new instrumentation to decipher the structure of galaxies
Johan Knapen (IAC/Liverpool)
3.45pm  C12

The faintest detectable parts of galaxies harbour an impressive amount of information about their evolution and even their formation. But reaching faint surface brightness levels means overcoming a number of severe challenges, including background analysis and light scattering. I will discuss these issues and highlight how we can use ultra-deep imaging to detect faint structures, including tidal arms, ultra-faint dwarf galaxies, and thick disks in edge-on galaxies. I will also discuss how upcoming surveys, including by Euclid and LSST, are bound revolutionise this field soon by allowing us to reach huge samples, as long as we can beat the systematics and handle the resulting streams of 'Big Data’.

Host: Tom P

23 Jan
Massive black holes along the cosmic history: formation, dynamics and gravitational waves
Alberto Sesana (Birmingham)
3.45pm  C12

Following detection by advance LIGO, gravitational wave (GW) stocks are on the rise. The low frequency GW Universe is likely dominated by signals emitted by a cosmological population of massive black hole binaries (MBHBs). I will review several aspect of MBH astrophysics, including their formation, evolution, interaction with their environment and GW emission. I will then discuss prospect of GW detection with pulsar timing arrays and/or future space based interferometers such as the laser interferometer space antenna (LISA) and for pulsar timing arrays.

Host: Jacob

06 Feb
Kinematic mapping and modelling of Early-Type Galaxies
Anne-Marie Weijmans (St Andrews)
3.45pm  C12

Host: Mick

13 Feb
Diversity, Engagement and Physics: How does it all come together?
Dominic Galliano (UCL)
3.45pm  C4

A Physicist has so many things to think about at the moment, before they can even get to their research! Public Engagement, Diversity, Widening Participation! They are all so important but can feel like a massive drag. In this talk, I’ll show how they come together and lead to benefits to your Physics. This talk will contain anecdotes and practical examples of projects from my career as a theoretical cosmologist, transport engineer, outreach officer at the IOP, Director of Public Engagement for a partnership of nine physics departments in the South-East and an LGBT+ in STEM campaigner. I’ll also have an update on the latest from the IOP / RAS / RSC’s LGBT+ workplace survey they carried out last year.

Host: Lizzie

22 Feb
Not-so-simple stellar populations in nearby, resolved massive star clusters
Richard de Grijs
3pm  C5

Until about a decade ago, star clusters were considered "simple" stellar populations: all stars in a cluster were thought to have similar ages and the same metallicity. Only the individual stellar masses were thought to vary, in essence conforming to a "universal" initial mass function. Over the past decade, this situation has changed dramatically. I will discuss my group's recent progress in this context, with particular emphasis on the properties and the alleged presence of multiple populations in Local Group star clusters across the full age range. Our most recent results imply a reverse paradigm shift, back to the old simple stellar population picture for at least some intermediate- age (~1—3 Gyr-old) star clusters, which opens up exciting avenues for future research efforts.

Host: Amy

27 Feb
VIPERS: The decline and fall of the most massive star-forming galaxies since z=1
Chris Haines (Birmingham)
3.45pm  C12

I present results from the recently completed VIPERS redshift survey which has obtained spectra for ~100,000 galaxies at z~0.5-1.2 over 24 square degrees, including >1000 star-forming galaxies with masses above 10^11Msun. I show how the number density of such massive star-forming galaxies has declined five-fold since z~0.8, and how the high-mass limit for the main star-forming sequence has fallen steadily to lower masses over the last 8 billion years. By examining in detail how the D4000 distribution of galaxies at fixed stellar mass has evolved, I show whether secular evolution can explain the observed decline in massive star-forming galaxies or if additional quenching events are required. We show that these massive star-forming galaxies at z~0.8 are the likely progenitors of local S0s.

Host: Roan

06 Mar
Preparing for JWST: What can we learn about high redshift galaxy evolution?
Emma Curtis-Lake (Cambridge)
3.45pm  C12

JWST will revolutionise our understanding of the evolution of high redshift galaxies. Where currently our understanding is limited to discrete samples selected by different mechanisms, with the largest samples derived from selecting galaxies from their rest-frame UV, we will be able to analyse galaxies from mass-selected samples using NIRCam/MIRI. Moreover we will have rest-frame optical spectroscopy using NIRSpec, with Halpha detected up to z~7, which is presently out of reach for current facilities. I will summarise some open questions of high-redshift galaxy evolution that count on future JWST data to disentangle, present the joint NIRCam and NIRSpec GTO survey plans as well as our publicly available mock catalogue designed specifically for survey planning. Finally I will show the results from a case study investigating to what accuracy can we derive physical properties from NIRSpec low-resolution spectra (R~100, covering 0.7-5 microns).

Host: Alex

13 Mar
Shedding light on gas around galaxies across cosmic time
Michele Fumagalli (Durham)
3.45pm  C12

Host: Sunny

20 Mar
Weak lensing beyond two-point statistics
Joachim Harnois-Deraps (Edinburgh)
3.45pm  C12

Massive international efforts are currently being deployed to construct predictions tools for upcoming weak lensing analyses, typically aiming at sub-percent precision. Their focuses are primarily set on two-point statistics (e.g. position and/or shape correlation functions), mainly because these can be directly related to the matter power spectrum, which can be accurately obtained from fitting functions and emulators. Weak lensing beyond the two-point statistics can play an important role however, for it has access to more cosmological information given that the matter density field has become non-Gaussian. In this talk I will review recent weak lensing data analysis based on higher order statistics, and discuss requirements for upcoming surveys, with a focus on the calibration with cosmological simulations.

Host: James

03 Apr
Radio stars are coming back, this time in color
Jan Forbrich (Hertfordshire)
3.45pm  C12

Host: Leonardo

15 May
Giant Broad-line Regions in Low-luminosity Active Galactic Nuclei
Nick Devereux (Embry-Riddle University)
3.45pm  C12

22 May
The galaxy-halo connection on the cosmic web
Rite Tojeiro (St Andrews)
3.45pm  C12

Galaxies and the halos in which they reside are intrinsically connected. That relationship holds information about important processes in galaxy and structure formation, and is key to unlocking the full statistical power of forthcoming redshift surveys and their cosmological analyses. In this seminar, I will consider how the galaxy-halo connection might depend on its position within the cosmic web - the familiar decomposition of large-scale structure in filaments, knots and voids - highlighting recent and ongoing work in observations and in simulations.

05 Jun
Galactic Archeaology - past, present and future
Sofia Feltzing (Lund University)
3.45pm  C12

12 Jun
The intuition in science
Jonathan Tallant (Nottingham)
3.45pm  C12

19 Jun
Galactic-scale outflows in galaxies of the local Universe
Guido Roberts-Borsani (UCL)
3.45pm  C12

10 Jul
What can we learn from chemical element abundances and their evolution in the Universe?
Jianhui Lian (Portsmouth)
3.45pm  C12

18 Jan
Weak lensing in the Dark Energy Survey: the photo-z issue
William Hartley (UCL)
3.45pm  Physics C12

The current frontier in cosmology is the charting of the accelerating expansion rate of the universe with time, and thereby characterising the phenomenology of dark energy. Doing so requires ambitious new surveys of galaxies over unprecedented volumes. The Dark Energy Survey is the largest ever galaxy survey and hopes to unlock the potential of gravitational weak lensing, amongst other methods, as a probe for cosmology. In this seminar, I will cover the early constraints that have been achieved on cosmology parameters from science verification data taken with the new DECam. A particular challenge for weak lensing analysis is in understanding the distances to the millions of survey galaxies. I will cover our approach taken during the science verification analysis and the future challenges we face in this aspect of the experiment.

Host: Miguel Socolovsky

08 Feb
Uncovering the First Stars
Emma Chapman (Imperial)
3.45pm  Physics C12

The Epoch of Reionization signals the end of the Dark Ages of the Universe and the birth of the first stars. The race is on to make the first statistical detection of this epoch however the foregrounds swamp the cosmological data by several orders of magnitude and their removal remains a significant challenge for both current and future telescopes. I will speak broadly about the foreground mitigation techniques currently being used with EoR data and take a closer look at the efforts being made by LOFAR with blind foreground removal methods.

15 Feb
A submm view of normal' distant star forming galaxies
Kristen Coppin (Herts)
3.45pm  Physics C12

Lyman Break Galaxies (LBGs) are the largest population of high-redshift (z > 3) star forming galaxies and as such provide valuable insights into the mass assembly of normal galaxies during the first few Gyr of the Universe. They have moderate star formation rates (~10s-100s Msun/yr) and ~10-100x higher space densities than the more extreme submillimetre galaxy population, thus they should comprise a significant portion of the far-infrared background at high redshift. But determining their true contribution to the far-infrared background has been difficult due to the rather large uncertainties that go hand-in-hand with deriving dust corrected UV luminosities and star formation rates. The only reliable way of measuring the dust content of LBGs is directly through submillimetre observations. In this talk I will present some new results on LBGs selected at z~3, 4, and 5 from a series of different studies using SCUBA-2, Herschel and ALMA.

Host: Tom Peterken

01 Mar
Exploring the early Universe with the largest emission-line surveys
David Sobral (Lancaster)
3.45pm  Physics C12

I will present new results regarding the first ~2 Gyrs of cosmic time using very wide-field Lyman-alpha (Lya) narrow-band surveys, including a large, matched Lya-Halpha survey to investigate how Lya and Lyman-continuum (LyC) photons escape from typical star-forming galaxies at high-redshift. We find that large Lya halos are ubiquitous in star-forming galaxies, and that the typical escape fraction of Lya and LyC photons is typically below a few percent. However, the escape fractions of Lya selected sources are significantly higher. We also find a much higher space density of very luminous Lyman-alpha emitters all the way from z~2 to z~7 than previously assumed, which we confirm spectroscopically with Keck, VLT and WHT. Many of our sources show high-ionisation lines in the rest-frame UV (CIII], CIV, HeII), and some have clear Lya blue wings. At z~7 our sources (e.g. CR7) show signatures of PopIII-like stellar populations (extremely metal poor) and/or direct collapse black holes and provide interesting challenges ahead of the launch of JWST. Our results also show that the steep drop in the Lya luminosity function into the epoch of re-ionisation happens only for the faint Lya emitters, while the bright ones likely ionise their own local bubbles very early on, and thus are visible at the earliest cosmic times.

Host: Rachana Bhatawdekar

08 Mar
Cosmological hydrodynamical simulations of the galaxy population
Rob Crain (LJMU)
3.45pm  Physics C12

I will briefly recap the motivation for, and progress towards, numerical modelling of the formation and evolution of the galaxy population - from cosmological initial conditions at early epochs through to the present day. I will focus in particular on the EAGLE simulations. They represent a significant development in this arena, since they broadly reproduce key properties of the evolving galaxy population, and do so using energetically-feasible feedback mechanisms. I shall present a broad range of results derived from EAGLE analyses, concerning the evolution of galaxy masses, their luminosities and colours, and their atomic and molecular gas content. I hope to convey some of the strengths and limitations of the current generation of numerical models.

Host: Jake Arthur

15 Mar
Star-formation and nuclear activity in galaxies: A perspective in the legacy era of the Herschel Space Telescope
David Rosario (Durham)
3.45pm  Physics C12

The far-infrared Herschel Space Observatory has opened our eyes to the cold dusty Universe. Far-IR wavelengths provide arguably the best tracers for star-formation in active galactic nuclei (AGN), since luminous nuclear activity is rather inefficient at keeping dust cold. I will report on studies that bring together the very best modern multi-wavelength survey datasets, from the X-rays to the optical to the far-IR, aimed towards developing a coherent view of the growth of supermassive black holes (in AGN) in relation to the growth of stellar content in galaxies (through star-formation). These studies build on the newest advances in our knowledge of galaxy evolution across most of the Universe's history. I will demonstrate that a positive relationship between star-formation and AGN activity is now clearly seen to z > 2. However, the nature of this relationship supports weak or stochastic co-evolution, driven more by the smooth increase of gas content in normal galaxies over time rather than a dominant role of short, intense episodes, such as star-bursts or mergers. This has important implications for the connections between galaxies and the black holes that reside at their hearts.

Host: Rachel Asquith

22 Mar
Fuelling and feedback: quasar host galaxies in the high-redshift Universe
Manda Banerji (Cambridge)
3.45pm  Physics C12

Cancelled

Host: Charutha Krishnan

05 Apr
The inner and outer view of galaxies
Cristina Popescu (UCLan)
3.45pm  Physics C12

Galaxies contains dust, and this complicates our view of the stellar populations in optical and UV light. The position of the Sun close to the galactic plane does not provide a better viewpoint of our own galaxy compared to external galaxies - on the contrary, the situation is even worse. Nonetheless, both the outer and inner view of galaxies are needed. A powerful route to the inner make-up of galaxies is to decode their panchromatic spectral energy distribution, taking into account the direct and dust-reradiated components of stellar light. In this talk I will show recent progress in self-consistently modeling radiative processes in galaxies and in the Milky Way, including the high energy gamma-ray emission, in an attempt to lift the veil on our understanding of the fundamental process of galaxy formation and evolution.

Host: Martha Tabor

03 May
The dark matter halo mass spectrum of the Milky Way
Jason Sanders (Cambridge)
3.45pm  Physics C12

Cosmological simulations predict that massive dark-matter haloes are home to a spectrum of smaller, less massive haloes and gaining access to these low mass haloes gives important clues to the fundamental nature of dark matter. Measurements of the subhaloes are naturally only possible through observations of baryonic tracers. I will discuss two different tracers that will shed some light on the properties of the Local Group’s subhalo population. First, tidal streams are dynamically cold structures that are sensitive to close encounters with dark matter subhaloes. I will discuss recent progress in the modelling of tidal streams, how gaps in streams caused by subhaloes can be efficiently modelled and the current constraints from data. Secondly, many of the larger subhaloes are expected to be the hosts of the dwarf spheroidal (dSph) galaxies in the Local Group. I will discuss progress on non-spherical modelling of dSphs and how flattening can enhance or diminish the expected dark-matter annihilation signals from dSphs. I will close by discussing recent results on the shapes and alignments of the Local Group dSph population.

Host: Ross Hart

10 May
Unveiling extreme dusty star formation at z > 2
Julie Wardlow (Durham)
3.45pm  Physics B1

Over the past ~20 years the high-redshift Universe has been increasingly opened to scrutiny at far-infrared wavelengths, where cool dust emission from star-formation dominates. The dusty star-forming galaxies (DSFGs) and submillimeter galaxies (SMGs), selected at these wavelengths likely represent an important, but short-lived phase in the growth of massive galaxies. These DSFGs often have star-formation rates in excess of ~1000 solar masses per year and are confirmed beyond z~6, although their redshifts and high dust contents make them faint and difficult to study at other wavelengths. Using data from the Herschel Space Observatory I have obtained mid-infrared spectra of SMGs, probing the conditions in their ISM. I will present the results from this spectroscopy program as well as discuss other results from our systemically-selected sample of gravitationally lensed SMGs.

Host: Aaron Wilkinson

17 May
The formation of galaxy clusters
Nina Hatch (Nottingham)
3.45pm  Physics B1

Distant galaxy clusters are powerful laboratories for observing the hierarchical growth of large-scale structure, constraining cosmological parameters, and for studying the formation of galaxies. However, distant (z>1.5) clusters are extremely rare and faint, so locating and studying them poses a significant observational challenge. In this seminar, I will review the theory of cluster formation and present recent advances we have made in detecting and studying distant galaxy clusters.

Host: Miguel Socolovsky

24 May
Public astronomy
Marek Kukula (Royal Observatory Greenwich)
3.45pm  Physics B1

Universities and funding bodies now tend to agree that public engagement is something to be encouraged. But delivering successful public outreach while holding down a research career isn’t always an easy balance to strike. Marek Kukula, Public Astronomer at the Royal Observatory Greenwich explores some of the ways in which astronomers can engage with a wide variety of audiences including the general public, schools, specialist groups and the media, and looks at how museums and galleries can help to provide a platform for researchers via exhibitions, talks and cross-disciplinary approaches from high art to popular culture. He'll also try to address the question of how public engagement can help early-stage researchers to develop their careers both in outreach and in academia and, time permitting, will reveal how he teamed up with writer Simon Guerrier to explore The Scientific Secrets of Doctor Who. <br><br> <strong>Biography:</strong> Marek completed his PhD in Radio Astronomy at the University of Manchester's Jodrell Bank Observatory and then carried out research into quasars and galaxy evolution at Liverpool John Moores University, the University of Edinburgh and the Space Telescope Science Institute in Baltimore. He subsequently worked for the University of Edinburgh’s Office of Lifelong Learning and as Project Manager for Researchers in Residence, a UK-wide scheme to support early-career academics to work with secondary schools. As the Public Astronomer at the Royal Observatory Greenwich he is part of a team of astronomy education and outreach specialists who engage with the public, schools and the media. The role involves working with scientists, historians and artists to explore the cultural as well as the scientific impact of astronomical research. Marek is a judge on the Insight Astronomy Photographer of the Year competition and has curated several exhibitions, including Visions of the Universe, on the history and impact of astrophotography, at Royal Museums Greenwich in 2013 and dark frame/deep field at the Breese Little gallery in 2015, juxtaposing the work of six contemporary artists with vintage NASA photographs. He is the author of The Intimate Universe and the co-author of The Scientific Secrets of Doctor Who, both published in 2015.

Host: Rachel Asquith

07 Jun
Studying galaxy evolution using integral-field spectroscopy
Michele Cappellari (Oxford)
3.45pm  Physics B1

I will give an overview of what we learned in our understanding of galaxy evolution thanks to integral-field spectroscopy.

Host: Martha Tabor

14 Jun
Radio-loud AGN: a multi-scale perspective
Beatriz Mingo (Open University)
3.45pm  Physics B1

Active galactic nuclei are among the most powerful astronomical objects in the universe. Though usually located in the core of their host galaxies, their feedback has the potential to influence the dynamics and energetics of their hosts on large scales, even affecting their star formation history. Radio-loud sources, in particular, can efficiently transport energy, through relativistic jets, up to megaparsec scales, influencing cluster gas dynamics and cooling times. I will try to summarise the properties of these objects, why they are important to understand galaxy and cluster evolution, and what surveys and methods we are currently using to study them.

Host: Charutha Krishnan

21 Jun
Where do emission-line galaxies live at z~1?
Violeta Gonzalez-Perez (Portsmouth)
3.45pm  Physics B1

Emission line galaxies trace the cosmic star formation history and moreover, they are being used as tracers of the dark matter distribution up to z~1. We have use a state-of-the-art model of galaxy formation and evolution to study the properties of model emission line galaxies, in particular [OII] emitters. To mimic a range of surveys, we select model [OII] emitters by making cuts in [OII] line flux, optical magnitudes and colours. The model [OII] emitters have luminosity functions in reasonable agreement with observations at z~1. 95% of these model galaxies are centrals hosted by haloes with M halo > 10^11 Msun/h . In the model very few haloes contain more than one [OII] emitter that is a satellite galaxy. Confronting this result to available observations, suggests the need to revise the modelling of hot gas stripping in satellite galaxies. The mean halo occupation distributions of these model galaxies have a global shape typical of star forming galaxies. For central [OII] emitters we have identified that we can split the contribution of central galaxies to the mean halo occupation distribution into an asymmetric Gaussian for central disks and a step function plateauing below one for central spheroids.

Host: Miguel Socolovsky

28 Jun
A conclusive test of cold dark matter? (School Colloquium)
Carlos Frenk (Durham)
4.00pm  Physics B13

The "Lambda cold dark matter" (LCDM) cosmological model is one of the great achievements in Physics of the past thirty years. Theoretical predictions formulated in the 1980s turned out to agree remarkably well with measurements, performed decades later, of the galaxy distribution and the temperature structure of the microwave background radiation. Yet, these successes do not inform us directly about the nature of the dark matter. Indeed, there are competing (and controversial) claims that the dark matter might have already been discovered, either through the annihilation of cold, or the decay of warm, dark matter particles. In astrophysics the identity of the dark matter manifests itself clearly in the properties of dwarf galaxies, such as the satellites of the Milky Way. I will discuss predictions from cosmological simulations assuming cold and warm (in the form of sterile neutrinos) dark matter and show how astronomical observations can conclusively distinguish between the two.

Host: Michael Merrifield

04 Oct
A massive cluster in its youth: the fundamental plane, kinematics, and ages for cluster galaxies at z = 1.80
Laura Prichard (Oxford)
3.45pm  Physics C12

Galaxy clusters are the largest gravitationally bound structures in the Universe, and we know that early type galaxies (ETGs) are more common towards their centres. Clusters of galaxies are increasingly rare at early times, but are essential for understanding the formation of these massive structures and how they alter the fate of their member galaxies. However, long integration times on large telescope are required to constrain the stellar properties of these distant cluster ETGs. Now with the advent of the multiplexed near-infrared integral field instrument, the K-band Multi-Object Spectrograph (KMOS) on the Very Large Telescope, we can target the ETGs in these valuable high-redshift clusters more efficiently than ever. The KMOS guaranteed observing program, the KMOS Cluster Survey (KCS; P.I.s Bender & Davies), has enabled a study of cluster galaxies in overdensities spanning z = 1–2 through absorption-line spectroscopy obtained from 20-hour integrations. I will present KMOS spectra for 16 galaxies and Hubble Space Telescope photometry of the furthest KCS overdensity, JKCS 041, an ETG-rich cluster at z = 1.80. To determine stellar ages of the cluster galaxies, a scaling relation called the fundamental plane (FP) was constructed for seven galaxies in JKCS 041; the highest redshift FP for ETGs in a single cluster. The relative velocities of the galaxies derived from the spectra indicated an infalling group of galaxies, and we determined that these were significantly younger than the rest of the cluster members. Based on the galaxy dynamics, cluster morphology, and galaxy stellar age results, we concluded that JKCS 041 is in formation and consists of two merging groups of galaxies. Our results could link galaxy ages to large-scale structure for the first time at this redshift.

18 Oct
Studying the expansion of the Universe with quasar spectra
Andreu Font-Ribera (UCL)
3.45pm  Physics C12

From 2009 to 2014, the Baryon Oscillation Spectroscopic Survey (BOSS) used the SDSS telescope to obtain spectra of 1.5 million galaxies to get very accurate measurements of the Baryon Acoustic Oscillations (BAO) scale at redshift z ~0.5. At the same time, BOSS observed over 184 000 high redshift quasars (z>2.15) with the goal of detecting the BAO feature in the clustering of the intergalactic medium, using a technique known as the Lyman alpha forest (LyaF). In this talk I will overview the final results from the LyaF working group in BOSS, including the measurement of BAO at z=2.4 both from the auto-correlation of the LyaF (Bautista et al. 2017), and from its cross-correlation with quasars (du-Mas-des-Bourboux et al. 2017). From the combination of these studies we are able to measure the expansion rate of the Universe 11 billion years ago with a 2% uncertainty. Starting in 2019, the Dark Energy Spectroscopic Instrument (DESI) will increase this data set by an order of magnitude. DESI will provide an exquisite measurement of the expansion over cosmic time, while at the same time addressing other interesting questions: the sum of the mass of the neutrino species, properties of dark matter particles, tests of general relativity and the shape of the primordial power spectrum of density fluctuations.

25 Oct
Understanding the bulge of the Milky Way
Victor Debattista (UCLan)
3.45pm  Physics C12

TBA

01 Nov
Caught in the act: charting galaxy transformation over cosmic time
Kate Rowlands (John Hopkins)
3.45pm  Physics C12

TBA

08 Nov
Accretion discs around massive stars: the revolution with ALMA
Katharine Johnston (Leeds)
3.45pm  Physics C12

TBA

22 Nov
Starbursts, normal galaxies and the cold gas history of the Universe
Mark Sargent (Sussex)
3.45pm  Physics C12

TBA

06 Dec
The spiralling signatures of planet formation
Farzana Meru (Cambridge)
3.45pm  Physics C12

TBA

13 Dec
Detecting and characterising exoplanets with direct imaging
Beth Biller (Edinburgh)
3.45pm  Physics C12

TBA

17 Jan
Connecting the initial conditions of star formation to their Galactic origins
Sarah Ragan (Cardiff)
3.45pm  Physics C12

Galactic plane surveys of the Milky Way in a variety of gas or dust tracers give us different perspectives on how the physical conditions of the interstallar medium vary throughout the Galaxy. The Herschel Infrared Galactic Plane Survey (Hi-GAL) covers the peak of the spectral energy distribution of dense, cold dust and thus supplies an essential part of the observational description of the conditions necessary for star formation in the Milky Way. With a catalogue of over 100000 compact Hi-GAL sources, I will discuss how star formation varies as a function of Galactocentric radius and proximity to spiral arms. This allows us to revisit several long-standing questions about the effect large-scale Galactic properties have on star formation on parsec scales. Moreover, with a comprehensive profile of the Milky Way over kiloparsec scales, these results provide a new detailed context in which to understand star formation in external galaxies.

Host: Martha Tabor

24 Jan
It came from outer space: Interstellar visitor 1I/‘Oumuamua
Colin Snodgrass (Open)
4.00pm  Physics C12

Late last year there was much excitement within the planetary science community, and in the press, about the first macroscopic interstellar object to be discovered passing through our Solar System. I'll tell the story of the discovery of 1I/'Oumuamua, the scramble to observe it before it left, and what we know about it after a couple of months of rapid publication of surprising results.

31 Jan
Supernova cosmology: not just 'w'
Ed Macaulay (Portsmouth)
3.45pm  Physics C12

TBA

14 Feb
Hard to find: compact galaxy relics and dwarf galaxies
Ivan Baldry (LJMU)
3.45pm  Physics C12

TBA

21 Feb
The role of gas flows in driving galaxy evolution: clues from the ISM
Amelie Saintonge (UCL)
3.45pm  Physics C12

TBA

07 Mar
Cosmic ray astrophysics in AGN outflows and supernova remnants
James Matthews (Oxford)
3.45pm  Physics C12

TBA

14 Mar
Strong lensing with ALMA
Simon Dye (Nottingham)
3.45pm  Physics C12

TBA

21 Mar
Investigating environmental and secular quenching with SDSS-IV: MANGA
Ashley Spindler (Open)
3.45pm  Physics C12

TBA

02 May
Can supernovae be an important source of dust for the ISM of galaxies?
Mikako Matsuura (Cardiff)
3.45pm  Physics C12

TBA

09 May
Extreme variability in AGN
Andy Lawrence (Edinburgh)
3.45pm  Physics C12

Variability in Active Galactic Nuclei has been seen as a defining feature for many years, and has long been seen as problematic for accretion disc theory. However, recent observations of extreme variabiity - factors of many over years - have brought these problems to a crisis. I will summarise the key observations, and examine in turn three possible explanations - microlensing events, tidal disruption events, and accretion disc instabilities.

16 May
Dusty star-forming galaxies at high redshift
Elizabeth Cooke (Durham)
3.45pm  Physics C12

TBA

23 May
Using globular cluster stellar populations to understand galaxy formation
Chris Usher (LJMU)
3.45pm  Physics C12

TBA

06 Jun
It came from outer space: interstellar visitor 1l/'Oumuamua
Colin Snodgrass (Open)
3.45pm  Physics C12

TBA

13 Jun
Resolved star formation at cosmic noon
John Stott (Lancaster)
3.45pm  Physics C12

TBA

20 Jun
Results from the JCMT Gould Belt and Transients surveys of local star formation
Jennifer Hatchell (Exeter)
3.45pm  Physics C12

TBA

20 Jan
Studying Cosmology with clusters: a miracle cure or a mug's game?
Kathy Romer (Sussex)
3.45pm  Physics C12

Using examples from the XMM Cluster Survey, the Dark Energy Survey, ITV's "Take Me Out", and BBC Three's "Don't Tell the Bride", I will demonstrate the importance of clusters of galaxies to modern Observational Cosmology and some of their down sides. Recent publications to be featured include: The redMaPPer Galaxy Cluster Catalog From DES Science Verification Data; Comparing Dark Energy Survey and HST-CLASH observations of the galaxy cluster RXC J2248.7-4431: implications for stellar mass versus dark matter; The XMM Cluster Survey: The Halo Occupation Number of BOSS galaxies in X-ray clusters; The XMM Cluster Survey: evolution of the velocity dispersion -- temperature relation over half a Hubble time; Crowdsourcing quality control for Dark Energy Survey images; OzDES multifibre spectroscopy for the Dark Energy Survey: first-year operation and results; The XMM Cluster Survey: testing chameleon gravity using the profiles of clusters; Galaxies in X-ray Selected Clusters and Groups in Dark Energy Survey Data I: Stellar Mass Growth of Bright Central Galaxies Since z~1.2. No Likey? No Lightie [where "Lightie" in this context translates to "well, you can always try using weak lensing, but that's a whole other can of worms"]!

Host: Rebecca Kennedy

10 Feb
From kinematics to shapes: understanding how environment affects galaxy morphology
Ryan Houghton (Oxford)
3.45pm  Physics C12

A galaxy's visual morphology is primarily determined by its stellar orbits and thus its assembly history. Stars in ordered rotation likely originate from the circular orbits of a gas-disk, while the disordered orbits in bulges reflect more complex formation histories. But while late-type galaxies are easily identified, subtle differences between early-type galaxies (ETGs) are not: a near face-on axisymmetric disk of old stars in a lenticular (S0) looks similar to a genuine ellipsoidal distribution of stars in an elliptical (E). However, integral field spectroscopy can distinguish the kinematics of disks (Fast Rotators, FRs) from ellipsoids (Slow Rotators, SRs): the SAURON & ATLAS3D surveys found that 66% of visually-classified Es contained ordered disk-like rotation and were thus misclassified S0s. With ETGs more common in denser environments, we extend this kinematic classification to the Coma and Abell 1689 galaxy clusters. Although SRs are found in the cluster centres, virtually none are found in the outer regions. Remarkably, the total SR:ETG ratio in each cluster was the same as in the (ATLAS3D) field, just 15%. Revisiting Dressler's original visual galaxy morphologies in 55 clusters we show that a similar result holds: the total E:ETG fraction in each cluster is 30%. Using the statistics from ATLAS3D, we show that these results are equivalent.

Host: Berta Margalef

17 Feb
The Dark Energy Survey: more than Dark Energy
Ofer Lahav (UCL)
3.45pm  Physics C12

The talk will present new expected and unexpected results from the Dark Energy Survey beyond cosmological studies, including solar system objects, Milky Way companions, galaxy evolution, galaxy clusters, high-redshift objects and gravitational wave follow ups (Reference: arXiv:1601.00329).

Host: Cristina Furlanetto

02 Mar
Planetary transits and young eclipsing binaries with the K2 mission
Suzanne Aigrain (Oxford)
3.45pm  Physics C12

The Kepler space mission revolutionised exoplanet science by discovering thousands of transiting planets, but the loss of two of its four reaction wheels put an end to the original mission a little over 2 years ago. Luckily, the satellite has been given a new lease of life, in the form of the K2 mission. K2 uses the Kepler satellite to observe 4 fields per year, near the Ecliptic plane, with only slightly reduced photometric precision compared to the original Kepler data, enabling it to survey thousands of particularly interesting targets for planetary transits: bright FGK stars, low mass M-stars, and stars in young open clusters. I am particularly interested in the latter, as it is the first time that we can perform efficient transit surveys in open clusters, and each detected system provides a unique constraint on evolutionary models for low-mass star or planets. In my talk I will give an overview of how we detect, confirm and characterise transiting exoplanets and young binaries with K2. The main challenges include dealing with the systematics effects caused by the reduced pointing accuracy of the satellite, the enhanced variability of young stars, and the challenges of measuring precise radial velocities for planet candidates around active stars. I will give a brief overview of the young eclipsing binaries and candidate planets found by K2 so far, and outline the rich prospects for open cluster science with future missions such as TESS and PLATO.

Host: Rachana Bhatawdekar

16 Mar
AGN-driven outflows, stellar feedback and starvation: the multiple routes to quench star formation in galaxies
Roberto Maiolino (Cambridge)
3.45pm  Physics C12

Understanding the process responsible for transforming star forming galaxies into passive and quiescent systems is currently one of the hottest topics in astronomy. I will discuss recent observational results probing different mechanisms at work in different galaxies and at different epochs. I will present multi-wavelength observations providing evidence that powerful starburst-driven and AGN-driven outflows have a profound impact on the evolution of galaxies, both locally and at high redshift; however such massive outflows may not be able to completely quench star formation in galaxies and actually, in some cases, such outflows can even boost star formation. I will show that the analysis of the stellar metallicities in large samples of local galaxies reveals that “starvation” (or “strangulation”, i.e. the lack of gas inflows) is actually responsible for quenching star formation in most galaxies. I will discuss the possible mechanisms responsible for the starvation of galaxies. I will also present some recent results from the ongoing Manga-SDSSIV survey, which is delivering integral field spectroscopy for thousands of galaxies. Based the analysis of the initial sample of several hundred galaxies I will show evidence that the quenching process in galaxies occurs predominantly inside-out, and I will show that even this observational finding can be explained in terms of “starvation”.

23 Mar
The faintest galaxies as probes of cosmology and galactic evolution
Michelle Collins (Surrey)
3.45pm  Physics C12

As the faintest galaxies we are able to observe in the Universe, the dwarf spheroidals can be thought of as the fundamental galactic unit. Within our Local Group, we are able to study these objects in extremely high detail, resolving their mass profiles, chemistries, and evolutionary histories. These measurements have led to several surprising results. One is that the masses of these systems appear to be lower than predicted by cold dark matter simulations. Additionally, dwarf galaxies are not distributed isotropically around their hosts, as naively expected in the current cosmological paradigm. In this talk, I will discuss these observational peculiarities, and how we may account for them, using examples of interesting dwarf galaxies in the Andromeda system, and results from recent hydrodynamical simulations.

Host: Aaron Wilkinson

27 Apr
Metal-poor galaxies throughout the cosmic ages
Bethan James (Cambridge)
3.45pm  Physics C12

The exploration of young and metal-poor galaxies across cosmic history is key to deciphering how fundamental processes such as enrichment, feedback, and star formation operated in the first galaxies. However, the spatially-resolved spectroscopic observations that are needed to constrain these physical mechanisms are currently extremely difficult, if not impossible, to perform because the objects are so faint and small. In this talk I will describe several new observing campaigns that resolve this issue by connecting low-metallicity star-forming galaxies in the nearby Universe with distant strongly-lensed galaxies as proxies for the earliest galaxies, including a newly discovered population of young, extremely metal-poor blue diffuse galaxies. I will discuss how the maps of star formation, ionisation, metallicity, and gas kinematics obtained from these observations currently constrain galaxy formation models (including the so-called bathtub' and `galactic fountain' models), and I will highlight future observational capabilities that will push our understanding of galaxy evolution to even smaller physical scales and earlier times.

Host: Ross Hart

04 May
A new approach to simulations of galaxy formation and cosmic large-scale structure
Andrew Pontzen (UCL)
3.45pm  Physics C12

I will start with an overview of the state-of-the-art in galaxy formation and large-scale-structure numerical simulations from cosmological initial conditions. On the one hand we wish to simulate large volumes to gain representative samples of galaxies and to understand the cosmological implications of forthcoming survey data from LSST, Euclid and DESI. On the other, we also want to maintain very high resolution to resolve highly non-linear astrophysical processes and internal kinematics for forthcoming galaxy IFU studies like MaNGA. These two requirements result in a tension on how to best spend limited computer time. I will argue that a new approach to simulations, in which we use statistical models to tailor cosmological initial conditions for different questions, can help relieve this tension. I will show a range of applications from large scale power spectrum estimation to galaxy quenching.

Host: Jake Arthur

11 May
Galaxy bimodality and post-starburst galaxies
Vivienne Wild (St Andrews)
3.45pm  Physics C12

Post-starburst galaxies have long been known as an intriguing class of galaxies, identified through their unusual optical spectra as having had a recent burst of star formation that has since quenched. What caused the starburst and what caused the quenching? Originally identified in clusters (so-called E+A or K+A galaxies), they are now known to exist in all environments. They are rare at low-redshift, but increasingly common at high redshift. I will review recent progress in studying post-starburst galaxy properties, focussing on the question of whether they are true “transition” species i.e. galaxies transiting from the blue cloud to the red sequence, and how important they could be for accounting for the growth of the red sequence since z~2.

Host: Miguel Socolovsky

18 May
The rosy present and golden future of strong gravitational lensing
Stephen Serjeant (Open University)
3.45pm  Physics C12

Gravitational lensing has seen a surge of interest in the past few years. Lensing is one of the very few probes capable of mapping dark matter halo distributions. Lensing also provides independent cosmological parameter estimates and enables the study of galaxy populations that are otherwise too faint for detailed study. The handful of strong lensing systems known in the year 2000 has now been replaced with hundreds, thanks to innovative multi-wavelength selection, and there is an imminent prospect of thousands of lenses from Herschel and other sub-millimetre surveys. I will show how Euclid and the Square Kilometre Array promise tens or even hundreds of thousands of strong lensing systems, and some early results from our long-term project on the 10m Southern African Large Telescope, which is extremely well placed to have an enormous impact in follow-up observations of foreground lenses and background sources.

Host: Cristina Furlanetto

01 Jun
The complex relationship between AGNs and their host galaxies
James Mullaney (Sheffield)
3.45pm  Physics C12

Active Galactic Nuclei (AGNs) are amongst the most powerful individual objects in the Universe. Powered by material accreting onto supermassive black holes at the centres of galaxies, the energy released by AGNs is widely thought to have played a major role in shaping today's galaxies. Despite their importance, fundamental questions still surround many aspects of AGNs, not least what governs their accretion rate (and thus power output) and how - or indeed whether - they influence their host galaxies. In this talk, I will summarise the exciting progress that has been made in both these areas of AGN astronomy over the past decade, while highlighting what key questions still remain to be addressed.

Host: Berta Margalef

08 Jun
Star Formation in the Cosmological Context (School Colloquium)
Robert Kennicutt (Cambridge)
4.00pm  Physics B13

It is now clear that the conversion of interstellar gas to stars, along with the subsequent feedback from massive star formation are fundamental agents in the shaping, evolution, and formation of galaxies. Thanks to a wealth of new multi-wavelength observations from the ground and space our empirical understanding of these processes is being revolutionised, yet our understanding of the underlying physical processes which trigger and regulate large-scale star formation remains embryonic. This talk will review what we have learned in the past decade about the demographics and diversity of star formation in galaxies, its evolution over cosmic time, and the empirical correlations and scaling laws that offer clues to deeper underlying physical processes of star formation and galaxy evolution.

Host: Alfonso Aragón-Salamanca

15 Jun
The high-speed universe
Vik Dhillon (Sheffield)
3.45pm  Physics C12

One of the best ways of studying compact objects in the Universe, such as white dwarfs, neutron stars, stellar-mass black holes, exoplanets and Solar System objects, is through their brightness variations. These tend to occur on timescales of seconds and below, and hence require specialised astronomical instrumentation. In this talk, I shall review the design and scientific highlights of the high-speed cameras ULTRACAM, ULTRASPEC and HiPERCAM, the first two of which have been in operation for over a decade, and the last of which is due to see first light next year on the largest optical telescope in the world.

21 Jun
The role of ram-pressure stripping in the shaping of galaxies
Yara Jaffé (ESO Santiago)
3.45pm  Physics C12

In a hierarchical Universe clusters grow via the accretion of galaxies from the field, groups and even other clusters. As this happens, galaxies lose their gas reservoirs via different mechanisms, eventually quenching their star-formation. One of the most effective mechanisms in clusters is ram-pressure stripping by the intra-cluster medium. I will present recent results from multi-wavelength observations of z<0.2 clusters that are helping to constrain the efficiency, time-scale, and consequences of stripping. In particular, I will present a phase-space analysis of HI-stripping and star formation in cluster galaxies, and show recent MUSE/VLT observations of the most extreme examples of stripping, the so-called "jellyfish galaxies".

Host: David Maltby

05 Oct
Picking apart blended FIR sources in the COSMOS field
Jillian Scudder (Sussex)
3.45pm  Physics C12

Observing galaxies in the Far-Infrared (FIR) gives us a unique window into the star formation rates of very high redshift, dusty galaxies. These galaxies are generally thought to be forming stars at a prodigious rate, heating their dust content, which then radiates in the FIR. However, observing this glow is difficult, even with a space-based telescope such as the Herschel Space Observatory, as the resolution of the images returned is quite poor. It is often assumed that a bright source in the FIR belongs to a single, highly star forming galaxy, but this is impossible to verify with low resolution images. In this talk I will discuss a new method of unpicking a single FIR detection into individual galaxies, and what the results of this unpicking imply for our understanding of galaxies in the early Universe.

12 Oct
Prospects for weak lensing with future radio surveys
Michael Brown (Manchester)
3.45pm  Physics C12

I will present a selection of results and ongoing projects in radio weak lensing. I will present forecasts which suggest that the SKA will be capable of world-leading weak lensing cosmology, potentially providing additional information to help remedy a number of systematics which could limit optical and near-IR weak lensing. In addition, cross-correlating cosmic shear measurements between optical and radio bands gives comparable constraints and should be free of many wavelength-dependent systematics. In order to achieve this promise, many challenges need to be solved and I will discuss a few of them. Outstanding questions include how to measure shapes from radio interferometer data, how to model the source galaxy population at faint micro-Jy fluxes, and how to estimate their redshifts. I’ll also discuss a number of radio weak lensing pathfinder surveys on which we are developing and training the required new analysis techniques.

Host: Rachel Asquith

19 Oct
The rise and fall (and rise again) of NGC1275
Alastair Edge (Durham)
3.45pm  Physics C12

Recent observations have shown that the properties of the dense intracluster gas cooling in the cores of clusters of galaxies are significantly affected by AGN activity in the central brightest galaxy. I will review these observations and focus on the most nearby example of this AGN Feedback from NGC1275 at the core of the Perseus cluster.

Host: Mehdi Walji

02 Nov
The dark hearts of galaxies: molecules as dynamical probes of galaxy evolution
Timothy Davis (Cardiff)
3.45pm  Physics C12

In this talk I will describe how mapping the dynamics of molecular clouds in the centre of galaxies can help us to constrain a wide range of astrophysical problems. From the enigmatic relation between galaxies and their supermassive black holes, the suppression of star-formation in dying galaxies, and the puzzling variation of the stellar initial mass function, molecules provide an ideal probe that can help us make progress. I will show how high resolution observations (with CARMA and ALMA) can be used to estimate the masses of supermassive black holes in galaxies across the Hubble sequence, and describe the WISDOM project, that aims to use this technique to constrain the importance of accreting SMBHs in galaxy quenching. I will show that the deep potential wells of massive galaxies can play an important role in quenching star-formation, transitioning galaxies as they grow from star-forming to "red and dead". Finally I will show how one can use molecules to probe the controversial topic of variation in the stellar initial mass function.

Host: Martha Tabor

09 Nov
Bright galaxies in the first billion years: exploring the prevalence and properties of star-forming galaxies at z > 6
Rebecca Bowler
3.45pm  Physics C12

Studying galaxies at high redshift (z > 6) provides a unique insight into the early stages of galaxy formation and evolution. The samples of star-forming galaxies discovered during this epoch have largely come from deep HST surveys, with wider-area ground-based data providing key constraints at the bright end. I will present our results from two degree scale near-infrared surveys (UltraVISTA/COSMOS and UDS/SXDS), looking at the bright-end of the luminosity function at z = 6 and 7. Studying the galaxies in more detail with Spitzer and HST, we find evidence for strong rest-frame optical emission lines such as [OIII] and a clumpy/merger-like morphology for the brightest objects. I will end with a discussion of our new analysis of the strong Lyman-alpha emitter, and potential Pop III candidate, CR7.

Host: Charutha Krishnan

17 Nov
NASA's Next Astrophysics Flagship: The Wide Field Infrared Survey Telescope (WFIRST)
Jason Rhodes (NASA JPL)
3.45pm  Physics C12

The top recommendation for a large space mission in the US 2010 Decadal Survey was the Wide Field Infrared Survey Telescope (WFIRST). Similarities in hardware requirements between proposed dark energy, exoplanet microlensing, and near infrared surveyor missions allowed for a single mission that would accomplish all three goals. The gift of an existing 2.4 meter telescope to NASA by another US government agency allowed for the addition of a coronagraph that will take images and spectra of nearby exoplanets; this instrument will be a technological stepping stone to imaging other Earths in the 2030s. I will give an overview of WFIRST's proposed instrumentation, science goals, and implementation plan.

Host: Rachana Bhatawdekar

23 Nov
The transformation of galaxies in the distant Universe
Omar Almaini (Nottingham)
3.45pm  Physics C12

In recent years there has been tremendous progress in identifying large samples of distant galaxies, but many crucial aspects of galaxy formation remain poorly understood. In particular, we still do not understand why star formation was abruptly quenched in many massive systems at high redshift. It is also unclear if the same processes are linked to the morphological transformation of galaxies, to produce the Hubble Sequence we see today. I will discuss recent observational and theoretical progress in this area, and present new evidence suggesting that the key transformative processes are intimately linked; for the most massive galaxies at least, the quenching of star formation appears to occur during (or very shortly after) the event that forms the compact proto-spheroid.

Host: David Maltby

07 Dec
HI-MaNGA: HI follow-up for the MaNGA survey
Karen Masters (Portsmouth)
3.45pm  Physics C12

Mapping Nearby Galaxies at Apache Point Observatory (MaNGA, part of the fourth incarnation of the Sloan Digital Sky Surveys or SDSS-IV), is partway through it's ~6 year programme to obtain spatially resolved spectral maps for ~10,000 nearby galaxies selected from the SDSS Main Galaxy Sample. These data will unwrap the layers of local galaxies - revealing their stellar and gas dynamics, as well as the ages and chemical make-up of their constituent stars, and locations of current star formation. MaNGA began observations on the Sloan Telescope at APO in July 2014 and is now the largest sample of resolved spectroscopy in the world, with ~3300 galaxies observed to date. MaNGA will provide an amazing census of the stellar and ionized gas content of galaxies for a representative sample of nearby galaxies. However, complementary information about the cold gas content is crucial for a number of applications, but especially understanding the physical mechanisms that regulate gas accretions and quench galaxy growth. In this seminar I will describe the HI-MaNGA project which is one of the follow-up projects for MaNGA focused on learning about cold gas components. For HI-MaNGA we have been awarded almost 1000 hours of time on the Robert C. Byrd Green Bank Telescope (in West Virginia) to obtain 21cm HI (neutral hydrogen) global profiles of ~600 MaNGA galaxies. I will explain how measuring the total HI content of MaNGA galaxies can add to our understanding of the physical mechanisms regulating star formation in galaxies, as well as show some interesting early results from the project.

Host: Ross Hart

14 Dec
Gravitational wave astrophysics: the future is now
Ilya Mandel (Birmingham)
3.45pm  Physics C12

The first detections of gravitational waves from binary black hole mergers have opened up new opportunities and challenges in astrophysics and fundamental physics. I will describe these recent discoveries and discuss advances in the analysis and interpretation of gravitational-wave observations. I will focus on my group's efforts to extract the astrophysical evolution of massive stellar binaries from observations of gravitational waves emitted during mergers of the stellar remnants.

Host: Miguel Socolovsky

14 Jan
The formation of galaxy clusters and the evolution of their galaxies at 0 < z < 2
3.45pm  Physics C4

Galaxy clusters are the most massive structures in the universe and their mass growth provides a unique test for cosmological models of structure formation. Clusters are also the location where many galaxies have their star formation strongly truncated, and this process is still poorly understood. I will present new results on the growth of stellar mass in clusters over ~10 Gyr of cosmic time which shows they are highly concentrated at early times and are growing in an inside-out manner, something that is not seen in most simulations. I will also present new constraints on the timescale and location for quenching of galaxies in the cluster environment at early times. These timescales are showing us that the process by which clusters quench star formation is likely evolving over cosmic time, and that we clearly need to invoke much more sophisticated models of environmental quenching and feedback in galaxies if we are to truly understand how galaxies evolve in high-density environments.

Host: Carl Mundy

21 Jan
Gas accretion and star formation: drivers of galaxy evolution
Amélie Saintonge (UCL)
3.45pm  Physics C4

Observations of molecular gas in distant galaxies are experiencing a coming-of-age, transitioning from a "discovery" to a "survey" mode. New and upgraded facilities are now making it possible to survey molecular gas efficiently in large galaxy samples, and these observations are proving to be critical in refining our general picture of galaxy evolution. In this talk, I will review recent results from the two largest surveys for molecular gas in normal star-forming galaxies, the z=0 IRAM-30m COLD GASS survey and the z=1-2 IRAM-PdBI PHIBSS survey, and show how they combine to lend strong support in favor of the "equilibrium" model for galaxy evolution, under which most of galaxy evolution is regulated by gas supply and the efficiency of the star formation process.

Host: Kshitija Kelkar

11 Feb
Global properties of stellar halos
Andreea Font (LJMU)
3.45pm  Physics C12

Stellar halos contain information about various stages of galaxy formation, from the incipient stages of in situ star formation to the later episodes of accretion and tidal disruption of dwarf galaxies. Recent gas-dynamical simulations suggest that the inner halo may be formed from the destruction of a previous galactic disc by merging with satellite galaxies or, less violently, by quasi-secular rearrangement of a proto-disc. The various mechanisms of halo formation leave different signatures in the present-day mass distribution of halo stars or in the spatial distribution of their chemical abundances. I will review the global properties of stellar halos from several recent gas-dynamical simulations and discuss the level of agreement among these and with the available observational data.

Host: Becky Kenneddy

4 Mar
The thermal and ionization history of the intergalactic medium: Confronting simulations with recent Lyman-alpha forest, Lyman-alpha emitter and CMB data
Ewald Puchwein (Cambridge)
3.45pm  Physics C12

We illuminate the thermal and ionization history of the intergalactic medium (IGM) by confronting cosmological hydrodynamical simulations of the IGM with the latest observational constraints on the IGM temperature, the statistics of Lyman-alpha emitters and the opacity of the Lyman-alpha forest, as well as with the latest Planck measurements of the Thomson scattering optical depth towards the CMB.

Host: Kenneth Duncan

11 Mar
Quenched galaxies in isolation
Samantha Penny (Portsmouth)
3.45pm  Physics C12

In this talk, I will discuss the result of a study of extremely isolated galaxies residing in voids in the Galaxy and Mass Assembly (GAMA) survey. While the majority of these galaxies are blue, star forming objects with (u-r) < 1.9, we identify a number of void galaxies with optical colours consistent with no ongoing star formation. A line strength analysis reveals these galaxies to have nuclear spectra consistent with old stellar populations. However, when the mid-IR colours of these galaxies are examined, we find that only void galaxies with masses > 10^10 Msun have truly passive stellar populations. Given their isolation, these highest mass void galaxies have likely undergone mass quenching.

Host: Carl Mundy

12 Mar
What shapes the local Universe galaxy luminosity function?
Nicolas Bonne (Monash)
3.00pm  Physics B17

Galaxy luminosity functions are used to measure the distribution of galaxy masses and star formation rates, and are thus critical for measuring galaxy growth and for constraining galaxy formation models. Though functions have been measured in many wavelengths, very little research has focused on what actually shapes the galaxy luminosity function, and as a result, many functions are fitted empirically rather than with physically motivated functional forms. To address this issue, we have measured luminosity functions which trace galaxy stellar mass, as well as functions which trace current star formation, as functions of galaxy morphology and of galaxy optical colour. As dark matter halo mass and stellar mass have a strong correlation, we show that functions of the two share a similar form. Star formation does not have such a clear correlation, and we propose a new method for fitting star forming luminosity functions by convolving models of the star formation rate duty cycle with functions of stellar mass.

Host: Carl Mundy

25 Mar
Short GRBs, kilonovae and gravitational wave sources
Nial Tanvir (Leicester)
3.45pm  Physics C12

Mergers of compact binaries involving neutron stars lie at the intersection of several key problems in astrophysics. They are widely thought to lead to short-duration gamma-ray bursts; to be an important production site for the nucleosynthesis of r-process heavy elements; and to emit strong gravitational wave (GW) signals that are the most promising for detection by the next "advanced" generation of detectors. Recently, the first evidence for kilonova emission, predicted to be produced by the radioactive decay of species created during such a merger, was found, associated with sGRB 130603B. I will review this discovery together with other observational constraints on the nature of sGRBs, and consider the prospects for kilonovae as electromagnetic signatures of GW events.

Host: Julian Onions

29 Apr
Biomedical signal processing: links to astronomy
Richard Bowtell (Nottingham)
3.45pm  Physics C4

Biomedicine and astronomy face similar challenges in dealing with increasingly large and complex data-sets which can include multi-modal, multi-spectral and multi-dimensional measurements. This presentation will address potential synergistic overlap of biomedical and astronomical signal processing approaches. I will particularly focus on magnetic resonance imaging (MRI) and magnetoencephalography (MEG), which are the techniques that underpin the research carried out at the Sir Peter Mansfield Imaging Centre, touching on data processing methods used in functional MRI, quantitative susceptibility mapping and measurement of resting state brain networks.

Host: Simon Dye

13 May
Building planetary systems
Richard Alexander (Leicester)
3.45pm  Physics C4

The last few years have seen an explosion in our knowledge of extra-solar planetary systems. We now know that exoplanets have an extraordinary range of properties, and almost every conceivable planetary architecture seems to exist in nature. Planets form in cold discs of dust and gas around young, newly-formed stars, and in this talk I will try to explain how such a diverse population of planets formed from these relatively homogenous initial conditions. I will first review the physics of protoplanetary disc evolution, and discuss the conditions under which planets form and migrate. I will show how disc evolution and dispersal influences migrating planets, leading to "deserts" and "pile-ups" in the distribution of exoplanets. I will then consider the new class of compact planetary systems discovered by Kepler, and discuss under what conditions it is possible to build these systems through migration. Finally I will present models of disc evolution in binary systems, and consider the fo rmation and dynamics of circumbinary planets such as Kepler-16b.

Host: Elizabeth Cooke

20 May
Hubble Frontier Fields: a new era for gravitational lensing
Mathidle Jauzac (Durham)
3.45pm  Physics C12

The Hubble Frontier Fields (HFF) initiative constitutes the largest commitment ever of HST time to the exploration of the distant Universe via gravitational lensing by massive galaxy clusters. This program devotes 140 orbits of HST time to deep imaging observations of each of six cluster lenses reaching m~29 (AB) uniformly in all pass-bands (10-30 orbits per filter - 3 ACS and 4 WFC3 pass-bands). The full set of data on Abell 2744 (z=0.308) has been taken in October-November 2013 with WFC3, and May-July 2014 with ACS. The second target, MACSJ0416.1-2403 (z=0.397) has been observed with ACS in January-February 2014, and with WFC3 in July-August 2014. I will present the new gravitational lensing pictures of these two complex systems using this exquisite set of data coming from the HFF program. We have demonstrated that we are now able to 'weight' these clusters' cores down to the percent level precision (recently published works), serving our quest for the high-redshift Universe.However, while the depth of these dataset makes these clusters amazing Cosmic Telescopes, it also enables us to get an unprecedented understanding of the cluster physics. Therefore, presenting the case of MACSJ0416 & Abell 2744, I will demonstrate the importance of such high-quality data to analyse the merging/dynamical history of the clusters themselves while comparing dark matter, light and gas distributions.

Host: James Nightingale

28 May
The evolution of satellite galaxy quenching
Sean McGee (Birmingham)
3.45pm  Physics C4

I will discuss observations of environmental quenching using spectroscopic redshift surveys from the local universe to redshift ~ 1.5. Ultimately, I will use these observations, together with numerical simulations, to infer how long it takes satellite galaxies to quench at a range of redshifts. This evolution of satellite quenching times gives important insights into the physical mechanism driving this quenching and into the general baryon cycle of galaxies.

Host: Lyndsay Old

03 Jun
The nature and environments of powerful WISE-selected AGNs
Andrew Blain (Leicester)
3.45pm  Physics C12

The WISE all-sky survey has discovered some of the most luminous dusty galaxies in the sky. Very powerful AGN, they appear to be surrounded by an excess of other powerful dusty galaxies that are similar to the submillimetre-selected galaxies SMGs. I will describe some of the features of the WISE-detected objects, and the potential for investigating them using ALMA and probing their role in reacting to and shaping their environments.

Host: Aaron Wilkinson

10 Jun
The state and mass of H2 gas in galaxies: a new emerging view
3.45pm  Physics C12

I will outline our past views regarding what it takes to find the mass of molecular hydrogen gas in galaxies, and what maintains the thermal and kinematic state of this, most important fuel for star-formation in the Universe. Then I will discuss how these views are now being dramatically revised, especially for vigorously star-forming galaxies, and outline the new paths of Interstellar Medium (ISM) research that have opened up as a result. ISM novices are especially welcome, for now is the time to start anew....

Host: Carl Mundy

17 Jun
External forcing in low and high redshift galaxies
Anna Cibinel (Sussex)
3.45pm  Physics C12

I will discuss the evolution of morphological and star-formation properties of galaxies focusing on two aspects: (1) the effect of environment on local group galaxies and (2) the frequency of major mergers vs. disk instabilities in high-z galaxies.

Host: Rebecca Kennedy

24 Jun
TBA
George Efstathiou (Kavli Institute for Cosmology)
4.00pm  Physics B13

Host: TBA

30 Sep
Star-forming galaxies at the cosmic dawn: lessons from Spitzer and UV spectroscopy
Renske Smit (Durham)
3.45pm  Physics C12

How the first generations of galaxies build up and how they bring the reionisation of the neutral gas in the intergalactic medium during the first Gyr of cosmic time remains one of the biggest questions in extragalactic Astronomy. While the launch of the James Webb Space Telescope will soon provide us with many new insights into this early epoch, we can already learn a lot about the properties of the earliest galaxies with use of current facilities. I will discuss how we can use extremely deep Hubble and Spitzer photometry in combination with rest-frame UV spectroscopy to further our understanding of early galaxy formation processes and the sources of ionising photons in the reionisation era.

Host: Rebecca Kennedy

07 Oct
Galaxy-scale feedback without AGN: detection of a molecular wind driven by stars
James Geach (Hertfordshire)
3.45pm  Physics C12

In traditional models of galaxy evolution, feedback associated with an active galactic nucleus (AGN) have been invoked as the standard channel to regulate stellar mass growth at the high end of the mass function. We have been investigating a sample of massive, compact galaxies that exhibit ultra-fast gas outflows (up to 2500 km/s) with no evidence of significant AGN activity. Recently we have shown that in at least one of these galaxies a significant amount of molecular gas is being driven out at speeds of up to 1000 km/s to scales of 10 kpc (Geach et al., 2014, Nature). I will discuss how this sample demonstrates that stellar feedback can be an effective channel for curtailing stellar mass growth in massive galaxies, and in particular the role of stellar radiation pressure as a mechanism for launching galaxy scale multi-phase super winds from high density star forming regions.

Host: Aaron Wilkinson

14 Oct
Cosmology and Galaxy Evolution with radio continuum surveys
Matt Jarvis (Oxford)
3.45pm  Physics C12

I will provide an overview of the current understanding of cosmology and galaxy evolution from radio continuum surveys, and show how this field will be revolutionised over the coming years, on the lead up to the SKA.

Host: Cristina Furlanetto

21 Oct
Weighing the Universe with the Lightest Elements
Max Pettini (Cambridge)
3.45pm  Physics C12

The nucleosynthesis of the lightest elements of the periodic table, hydrogen, helium, lithium and their isotopes, during the first few minutes of our Universe history is one of the cornerstones of the standard model of cosmology and particle physics. In the last few years, it has become possible to determine the primordial abundances of these elements with high precision, finally realising their long-appreciated potential for measuring the cosmic density of ordinary matter. In this seminar, I shall review the latest developments in the determination of the primordial abundance of deuterium in particular, using the technique of QSO Absorption Line Spectroscopy. The 'punch line' is that independent measures of the density of baryons at different cosmic epochs are in excellent mutual agreement. Such concordance places interesting limits on the existence of relativistic particles beyond the standard model of physics.

Host: David Maltby

04 Nov
How to model AGN feedback in cosmological simulations?
Debora Sijacki (Cambridge)
3.45pm  Physics C12

In this talk I will discuss which feedback mechanisms are needed to reproduce realistic stellar masses and galaxy morphologies in the present day Universe and argue that the black hole feedback is necessary for the quenching of massive galaxies. I will then demonstrate how black hole - host galaxy scaling relations depend on galaxy morphology and colour, highlighting the implications for the co-evolutionary picture between galaxies and their central black holes. In the second part of the talk I will present a novel method that permits to resolve gas flows around black holes all the way from large cosmological scales to the Bondi radii of black holes themselves. I will demonstrate that with this new numerical technique it is possible to estimate much more accurately gas properties in the vicinity of black holes than has been feasible before in galaxy and cosmological simulations, allowing to track reliably gas angular momentum transport from Mpc to pc scales. Finally, I will also discuss if AGN-driven outflows are more likely to be energy- or momentum-driven and what implications this has for the redshift evolution of black hole - host galaxy scaling relations.

11 Nov
The Galactic Plane as an object - results from IPHAS and related surveys
Janet Drew (Hertfordshire)
3.45pm  Physics C12

The INT Photometric H-alpha Survey of the Northern Galactic Plane (IPHAS) started in 2004 and is now complete apart from some updates to even out the data quality. The companion blue survey, UVEX, started a couple of years later and at the end of 2011 coverage of the Southern Plane, via VPHAS+ running on the VST, got underway. Between them, these surveys provide imaging in u,g,r,i and H-alpha of the complete Galactic Plane within the latitude range |b| < 5 degrees, down to at least 20th magnitude. In this talk, I will give some of the background on these surveys before focusing on a number of results from them that relate to the large scale properties of the plane of the Milky Way. These will include extinction mapping of the northern Plane and a comprehensive search for massive stars in the south.

18 Nov
Handling astrophysical uncertainties on WIMP direct detection
Anne Green (Nottingham)
3.45pm  Physics C12

Diverse astrophysical and cosmological observations indicate that most of the matter in the Universe is cold, dark and non-baryonic. Weakly Interactive Massive Particles (WIMPs) are generically a good dark matter candidate and particle physics provides us with a well-motivated WIMP candidate in the form of the lightest supersymmetric particle. WIMPs can be detected indirectly (via the products of their annihilation) or directly (via elastic scattering in underground detectors). After an introduction to WIMPs and their detection I will focus on direct detection experiments, in particular astrophysical uncertainties and how they can be addressed.

Host: Andrea Cicchini

02 Dec
Galaxies from the cores of clusters into the cosmic web
Kevin Pimbblet (Hull)
3.45pm  Physics C12

On the largest of scales, the Universe is organised in to a so-called "cosmic web" - with galaxies being funnelled along filaments that surround voids and in to the nodes of the web -- clusters of galaxies. As they do so, they evolve and change. The question of how galaxies form and evolve over time within the cosmic web is one that has been with us for many years now and research in this area has only accelerated and thrown up more issues as problems get solved and raise new ones. In this talk, I will outline my recent contributions to this field by examining how galaxies in the local Universe are evolving (or not) and how biases in certain datasets can affect the degree of confidence we have in galaxy evolution. I will show new results on the HI content of galaxies in the cosmic web taken from a unique marriage of the 6dFGS survey and HIPASS radio data and highlight our recent work on the Coma cluster that suggests a number of studies may be biased when using this cluster as a redshift=0 baseline to compare other higher redshift clusters to.

Host: Berta Margalef

09 Dec
Black holes at all scales: from stellar mass binaries to the biggest Quasars
Christine Done (Durham)
3.45pm  Physics C12

I will review what we know about the accretion flow in the stellar mass black hole binary systems, and show how we can use them to test Einstein's General Relativity in strong gravity. The resulting accretion flow models and their associated jet can be scaled up to the supermassive black holes to give some physical insight into the zoo of different types of AGN and Quasars.

Host: Rachana Bhatawdekar

22 Jan
Triggering Active Galactic Nuclei: Do mergers matter?
Carolin Villforth (St Andrews)
3.45pm  Physics C12

The discovery that supermassive black holes reside in the centers of most if not all massive galaxies has emphasized the importance of Active Galactic Nuclei (AGN) in galaxy evolution. Despite this, the processes that trigger Active Galactic Nuclei remain poorly understood. While low luminosity AGN require fuel supplies low enough to allow fueling through so-called secular processes, the gas masses required to power luminous AGN are so large that major mergers of gas-rich galaxies are likely the only triggering mechanisms. However, the observational evidence for a connection between mergers and AGN remains weak. I will present a HST CANDELS study analyzing AGN host galaxy morphologies in a sample of moderate redshift (z=0.5-0.8) AGN spanning a wide range of luminosities. I will discuss if and how the importance of mergers changes as a function of AGN luminosity.

Host: Ismarl Botti and Bruno Rodriguez

5 Feb
Building Spiral Galaxies: 73 Years of Failure and Counting
3.30pm  Physics B21

The history of disk galaxy simulation is dotted with remarkable successes, tempered by frustrating impasses, including an inability to recover anything remotely similar to the Milky Way. Recent advances suggest that we might have made a breakthrough by generating essentially bulgeless disks. I will examine the evidence for this new-found optimism and identify where the shortcomings suggest we should be concentrating our future efforts.

Host: Stuart Muldrew

12 Feb
Submillimeter Galaxies and Quasars as Probes of Galaxy Evolution
3.45pm  Physics C12

Some of the most extreme star formation in the Universe occurs in a population of dusty galaxies at z~2, selected at submillimeter wavelengths (SMGs). Resolved studies of the star forming gas and the fuel for the star formation in SMGs have provided extensive information about the origin of their properties and imply that these systems may be the progenitors of the massive galaxies in the local Universe. I will present observations of SMGs from Integral Field Units, used to study the ionised gas morphologies and dynamics, testing if they consist of merging components. I will then present the results from observing SMGs using millimeter interferometry to probe the molecular gas and the cold neutral interstellar medium, constraining the physical conditions within the SMGs. I will discuss the implications of these results on models of the evolution of massive galaxies. I will then explore the next stage of this evolution, from a merger induced starburst (the SMG phase) to a UV luminous quasar, by discussing observations of reddened quasars which may represent this transition phase.

Host: Stuart Muldrew

19 Feb
Star formation relations across the CO ladder and redshift
Thomas Greve (UCL)
3.45pm  Physics C12

We present FIR−CO luminosity relations (i.e., log LFIR = a log L′CO + b) for the full CO rotational ladder continuously from J = 1 − 0 up to J = 13 − 12 for a sample of 76 (Ultra) Luminous Infra- red Galaxies (LIR > 1E11Lsun) using date from Herschel SPIRE-FTS and ground-based telescopes. We extend our sample to high redshifts (z > 1), by including 49 (sub)-millimeter selected dusty star forming galaxies from the literature with robust CO observations, and sufficiently well- sampled FIR/sub-millimeter spectral energy distributions (SEDs) so that accurate FIR luminosities can be deduced. The luminous starbursts at high redshifts enlarge the range of the FIR−CO luminosity relations towards the high IR-luminosity end while adding more mid-J/high-J CO line data (J=5–4 and higher) that have been scarce until the advent of Herschel. The now much enlarged dataset (both in terms of IR luminosity and J-ladder) reveals linear FIR−CO luminosity relations (i.e., a ≃ 1) for J = 1 − 0 up to J = 5 − 4, with a nearly constant normalization (b∼2-2.5). This is expected from the also linear IR-(molecular line) relations recently found for the dense gas tracer lines, as long as the dense gas mass fraction does not vary strongly within our (merger/starburst)-dominated sample. However from J = 6 − 5 and up to the J = 13 − 12 transition we find increasingly sub-linear slopes and higher normalization constants the higher the J-ladder. We argue that these are caused by a new warm (∼100K) and dense (> 104 cm−3) gas component whose thermal state is not maintained by the SF-powered far-UV radiation fields (and thus is no longer tied to the SFR) and one that is increasingly present towards the high LIR end. The IR-normalized global CO SLEDs that remain mostly flat from J = 6 − 5 up to J = 13 − 12, and are a generic feature of the (U)LIRGs in our sample, further support the presence of such a gas component.

Host: Chris Conselice

5 Mar
The Missing Link Between the First Stars and the Last Stars
Britton Smith (Edinburgh)
3.45pm  Physics C12

It is well known that stars observed in the local universe form with something very close to a universal initial mass function (IMF) where the vast majority are of low mass. However, this cannot be the case for the very first stars to ever form as a similar IMF would yield many surviving to the present day, contradicting the fact that none have ever been observed. Theory and simulation have also suggested that the first stars likely had a more top-heavy IMF owing to their unique chemical makeup. This implies that a transition in star formation modes must have taken place at some point in the history of the universe. Like the formation of the first stars, this critical epoch exists outside of the range of direct observation and, as such, has been primarily the domain of theory. I will give a review of research into the formation of the first (Population III) stars and theories of the transition from Population III to modern-day star formation. I will then present new results from a set of simulations designed to directly simulate the conditions of this period. Finally, I will conclude with a discussion of the yt simulation analysis toolkit, whose aim is to become a lingua franca for astrophysical simulations by allowing researchers to focus on physical objects instead of files on disk, regardless of the simulation code they use.

Host: Lyndsay Old

12 Mar
Recent Results from the Local Cluster Substructure Survey
Graham Smith (Birmingham)
3.45pm  Physics C12

In principle galaxy clusters offer powerful constraints on the dark energy equation of state, and opportunities to test gravity theory. These exciting goals can only be achieved at a useful level of precision if the mass of galaxy clusters can be measured accurately. One of the main aims of the Local Cluster Substructure Survey is to calibrate clusters as cosmological probes as part of the global effort to characterise dark energy. I will present new results on cluster mass measurement from our programme of lensing, X-ray, and infrared observations of clusters at z=0.2, and discuss their implications for cluster cosmology. I'll also mention our work on galaxy evolution in clusters if time allows.

Host: Lyndsay Old

19 Mar
The physics and environmental impact of radio-galaxy jets
Judith Croston (Southampton)
3.45pm  Physics C12

Relativistic jets from active galactic nuclei are now known to play an important role in galaxy evolution in the nearby Universe, with their role at higher redshifts remaining uncertain. In the near future, deep extragalactic surveys with next-generation radio telescopes will lead to an unprecedented view of the low-luminosity radio jet population to high redshifts. Translating radio-galaxy population statistics into a robust understanding of the evolving role of radio jet feedback in galaxy evolution requires solving decades-old uncertainties in the physics, energetics and environments of radio-loud AGN. I will discuss recent advances in this subject, driven by the powerful combination of X-ray and radio observations, including early results from the Low-Frequency Array (LOFAR).

Host: Ismael Botti

2 Apr
Star Formation and the Role of Feedback
Anthony Whitworth (Cardiff)
3.45pm  Physics C4

The current wisdom is that stars form in molecular clouds as a consequence of turbulent fragmentation. I will discuss what constraints are placed on this theory by observation and what successes the theory has had in satisfying the constraints, the roles played by thermodynamics and feedback in regulating star formation, and the many problems that remain to be solved. I will illustrate, with SPH simulations, some of the processes that may be at work.

9 Apr
Weak gravitational lensing: beautiful and not-so-beautiful results
Alan Heavens (Imperial)
3.45pm  Physics C4

Studies of weak gravitational lensing on a cosmic scale are beginning to provide interesting results which are adding to our knowledge of cosmology, and there is promise of precise measurements of the properties of dark energy and modified gravity with future surveys. In this talk, I will show recent results related to CMB lensing and galaxy lensing, showing on the one hand beautiful agreement with theory, and on the other, an indication that things may be more complicated than we think.

Host: James Nightingale

14 May
TBC
Jean Brodie
2.00 pm  CAPT A113

14 May
TBC
3.45pm  Physics C4

Host: Ken Duncan

21 May
Populating Virtual Worlds with Real Observations: Earth Observation and Mapping Mars
Stuart Marsh (School of Geography, University of Nottingham)
3.45pm  Physics C4

In recent years, the concept of the Virtual or Digital Earth has gained currency and a new international society has been set up to develop it further. However, attention has focussed on the surface of the planet and it could be argued that the virtual Earth is hollow. Geologists are working through international initiatives such as the Group on Earth Observations to add the third dimension. The techniques used and the observations made are increasingly available for other planetary bodies, such as Mars, for which we have even less subsurface information. By developing methods to populate the Earth’s third dimension, we also develop ways to do this on Mars. The talk will set out some of this context and then describe ongoing and planned work in NGI and partner organisations that aims to address these challenges.

Host: Frazer Pearce

4 Jun
Probing the mass, structural, statistical, and environmental evolution of massive galaxies
Francesco Shankar (Southampton)
3.45pm  Physics C4

One of the most important, but still highly debated, issues in contemporary cosmology, is the formation and evolution of massive spheroidal galaxies. Extensive semi-analytic galaxy formation models (SAMs), still debate whether mergers have played a major role in the assembly of ellipticals, or other "in-situ" processes, such as strong, dissipative early bursts of star formation, and/or clumpy accretion, have played an equally important role. In this talk, I will discuss the global evolution of massive spheroids, adopting state-of-the-art SAMs, as well as advanced semi-empirical models. In particular, I will show that, at variance with several previous attempts, hierarchical models can faithfully reproduce the overall shape, normalization, and scatter of the local size-stellar mass relation for massive early-type galaxies as measured in SDSS. I will then move on discussing the role of progenitor bias and environment in the overall structural evolution of massive galaxies. I will conclude with the additional constraints obtainable from lensing measurements on the global profile of galaxies.

Host: Chris Conselice

11 Jun
The Decomposed Bulge-Disk Evolution of Massive Galaxies at $$1 \lt z \lt 3$$
Victoria Bruce (Edinburgh)
3.45pm  Physics C4

I will present results from bulge-disk decompositions of massive galaxies at $$1 \lt z \lt 3$$ in the CANDELS survey and discuss the implications of our findings within the context of some of the current models of galaxy evolution and quenching. By decomposing the galaxies in our sample according to their H(F160W)-band light fractions and extending this analysis across multiple bands, we have been able to conduct SED fitting of the separate components. In addition to morphological properties, this has provided us with individual component stellar-mass and star-formation rate estimates. These decompositions have allowed us to explore the evolution of the galaxies in our sample split into their bulge and disk, star-forming and passive sub-samples, and has provided new insight into the links between quenching and morphological transformations within these systems.

Host: Jamie Ownsworth

18 Jun
Scaling relations of small stellar systems
Duncan Forbes (Swinburne)
3.00pm  CAPT A113

Using new data from the Keck telescope I report on the scaling relations of small stellar systems, ie globular clusters, ultra compact dwarfs, dwarf and compact ellipticals. The elevated mass-to-light ratios seen in some of these systems may indicate either the presence of dark matter, central black holes or a bottom-heavy IMF. Various scaling relations are investigated to shed light on which of these interpretations is most likely. The origin of cEs and UCDs is also discussed.

Host: Ana Chies Santos

22 Aug
First Galaxies and DRAGONS
Alan Duffy (Swinburne)
1.00pm  CAPT A113

One of the most important questions in astronomy today is the source of the ionising photons that caused a predominantly neutral Early Universe to evolve into the ionised one we see today. I have investigated this Epoch of Reionisation with a a new suite of high resolution hydrodynamical simulations, created within the DRAGONS group. These simulations show that the galaxies observed at early times represent merely the tip of an iceberg; with a hidden population of faint galaxies that can Reionise the Universe with ease. Although the global star formation history of the early universe is strongly constrained by current observations, we actually know little about the nature of star formation at this time (as given by the specific star formation rate). I will demonstrate that we can understand these objects but need to push our observations deeper, a goal that will likely have to await the James Webb Space Telescope.

1 Oct
Stellar haloes of massive early-type galaxies at z~0.7 or how to use the HUDF for local Universe studies
Fernando Buitrago (Edinburgh)
3.45pm  Physics C12

The most massive galaxies (M_stellar > 10^11 M_sun) are still very mysterious objects because they display extremely small sizes (~1 kpc) at z > 1.5 and therefore a remarkable change in their observational properties is necessary to match them with their local Universe counterparts. In particular, their size-mass relation has been subject to a great debate because high redshift observations may lose the light from the extended low surface brightness galaxy outer parts. Thanks to the depth, resolution and careful data reduction of the Hubble Ultra Deep Field 2012 programme we are able to detect extended stellar haloes for the six massive Early-Type Galaxies (ETGs) located in this image at $$z \lt 1$$. We are able to measure reliably their surface brightness profiles out to ∼31 mag arcsec^−2 , which translates into >25 effective radii or >100 kpc for some objects in our sample, making our observations comparable to the nearby Universe studies but at much larger cosmic distances. Once the faint component is included in our analyses, it has only a reduced impact in the structural parameter estimations, reinforcing the reported compactness of the massive galaxy population at high-z. The presence of these extended stellar haloes, along with dim tidal features and a large number of galaxy satellites seem to be common for massive galaxies. HUDF images are not only useful for investigating the highest redshift galaxies but they also open up a window for the comprehension of the local Universe.

Host: David Maltby

8 Oct
Bayesian model comparison in Astronomy and Cosmology
Daniel Mortlock (Imperial)
3.45pm  Physics C12

Bayesian inference provides a self-consistent method of model comparison, provided that i) there are at least two models under consideration and ii) all the models in question have fully-specified and proper parameter priors. Unfortunately, these requirements are not always satisfied in astronomy and cosmology: despite the existence of exquisitely-characterised measurements and quantitative physical models (i.e., sufficient to compute a believable likelihood), these models generally have parameters without well-motivated priors, making completely rigorous model comparison a formal impossibility. Still, huge advances have been made in cosmology, in particular, in the last few decades, implying that model comparison (and testing) is possible in practice even without fully specified priors. I will discuss the above principles and then illustrate some test cases of varying rigour, outlining some schemes for formalising heuristic approaches to model testing within a Bayesian framework.

Host: Aaron Wilkinson

15 Oct
Evolution of gas and dust with Herschel ATLAS
Loretta Dunne (Canterbury, NZ)
3.45pm  Physics C4

I'll be presenting a study of galaxies in the Herschel-ATLAS local volume $$z \lt 0.05$$. We have found that most of the galaxies in the local volume are low surface brightness, blue and dust rich, with very cold dust temperatures. The average gas fraction of the dust selected sample is 0.5, which is very much higher than the average gas fraction of typical optically selected samples. I'll describe the properties of these sources and ask how representative they may be of galaxies in the early Universe.

Host: Cristina Furlanetto

22 Oct
Dissecting the Diffuse Gamma-Ray Background
Mattia Fornasa (Nottingham)
3.45pm  Physics C4

The Diffuse Gamma-Ray Background (DGRB) is the radiation that remains after the contribution of Galactic gamma-ray emission and extragalactic sources is subtracted from the total gamma-ray flux. The DGRB collects the radiation of all those sources that are too faint to be resolved individually and, thus, it represents an essential tool to study faint gamma-ray emitters like star-forming or radio galaxies and the exotic Dark Matter. I will review our current knowledge of the nature of the DGRB, presenting the strategies that have been proposed to study it. I will focus, in particular, to what we can learn from the measurement of its angular anisotropies.

Host: David Maltby

5 Nov
Cosmology from the polarized microwave background
Joanna Dunkley (Oxford)
3.45pm  Physics C12

The polarization of the Cosmic Microwave Background (CMB) has had significant attention this year in light of results from the BICEP2 experiment. I will review CMB polarization and describe how it can be used to test cosmic inflation via gravitational wave signatures. It can also be used to probe other features of the primordial universe, and to trace the cosmic web of dark matter via its gravitational lensing signal. I will describe the ACTPol experiment, currently in operation in Chile. It measures the CMB polarization at high resolution and overlaps with several optical large-scale structure surveys. I will show first results from data measured in 2013, and discuss prospects for cosmology. I will also describe preparations for the next stage Advanced ACTPol project, which will map the CMB polarization over half the sky at multiple wavelengths.

Host: Kenneth Duncan

12 Nov
Massive molecular gas flows and AGN feedback in galaxy clusters
Helen Russell (Cambridge)
3.45pm  Physics C4

Powerful radio jets launched by a central supermassive black hole pump a substantial amount of energy into their surrounding galaxies and cluster environment. This active galactic nucleus feedback is now thought to be the essential mechanism in galaxy formation models regulating galaxy growth by suppressing gas cooling and star formation. But many key questions remain, including how the black hole is fuelled, how the heating can be distributed over large scales yet closely coupled to the gas cooling rate and the role of the cold molecular gas apparently cooling from cluster atmospheres. I will present ALMA Early Science observations of molecular gas in the central galaxies of A1664 and A1835 which show spectacular 10 billion solar mass outflows driven out by the radio jets and a massive gas inflow settling into a disk around the nucleus.

Host: Kshitija Kelkar

19 Nov
Evolving and revolving: the relativistic jets of the black hole binary SS433
Katherine Blundell (Oxford)
3.45pm  Physics C4

Black holes in our Galaxy, such as those in the microquasars SS433 and Cygnus X-3, demonstrate dynamic behaviour in accretion and dramatic mass outflows. We observe winds and relativistic plasma jets to emerge from these objects which resemble the modes of mass-loss in the supermassive black holes of powerful quasars in the distant universe. Time-resolved observations of the accretion and subsequent mass-loss from microquasars offers great rewards in terms of information about the nature of these remarkable phenomena in the Universe. I will describe how combined multi-wavelength strategies across the electromagnetic spectrum continue to yield new discoveries and discuss how time-resolved observations have led to the discovery of a further mode of mass-loss in SS433 via a circumbinary disc. I shall present the exquisitely detailed behaviour of these modes of mass-loss before, during and after a major flare event in this object, with reference to comparable behaviour seen in similar objects.

Host: Elizabeth Cooke

3 Dec
On the interplay between star formation and feedback in galaxy formation simulations
Oscar Agertz (Surrey)
3.45pm  Physics C4

The origin of today’s Hubble sequence and the associated galaxy scaling relations are salient issues in modern astrophysics. In this talk I overview the current state of computational galaxy formation and discuss recent advances in the field. I will focus on results from recent state-of-the-art cosmological simulations where the locations of massive star clusters are beginning to be resolved. I illustrate the sensitivity of galaxy evolution to how star formation and stellar feedback proceeds on small scales in the interstellar medium, and discuss the role of “feedback regulated" star formation. In this context I demonstrate the role of stellar feedback, and emerging galactic winds, in controlling observables such as the baryon content of galaxies, galaxy sizes, gas and stellar metallicities, and the Kennicutt-Schmidt relation over cosmic time.

Host: Julian Onions

10 Dec
The Tarantula Nebula - A template for extragalactic star forming regions
Paul Crowther (Sheffield)
3.45pm  Physics C4

I will present results from two spectroscopic surveys of the LMC supergiant HII region 30 Doradus (Tarantula Nebula), namely the VLT-FLAMES Tarantula Survey (VFTS) in which the physical, binary and kinematical properties of 800 massive stars have been obtained, plus a HST/STIS census of the central R136 ionizing cluster. I will also compare our spatially resolved stellar census with the integrated properties of the giant HII region and R136 cluster - as would be witnessed if viewed from Mpc distances, relevant to determinations of ages and stellar mass functions of extragalactic star forming regions.

Host: James Nightingale

23 Jan
On the role played by cold filamentary gas flows in shaping (most) galaxies
Julien Devriendt (University of Oxford)
3.45pm  B13

stuff

20 Nov
Massive stars: From the VLT to the ELTs
Dr. Chris Evans
3.45pm  C23

Stuff

21 Nov
Nonlinear Structure formation in a warm dark matter universe
Aurel Schneider (University of Sussex)
3.45pm  C23

The warm dark matter (WDM) model is a promising alternative cosmological scenario. I will talk about WDM structure formation, addressing both numerical simulations and analytical approaches.

28 Nov
How do stars form?
Simon Goodwin (Sheffield)
3.45pm  C23

Star formation is a key problem in astronomy which impacts on galaxy formation and evolution, and sets the initial conditions for planet formation. I will talk about our current understanding of local, low-mass star formation. Firstly, how we think that bound star clusters form from smaller substructure. And also how binary observations suggest that star formation might vary from region to region even though the IMF stays the same. The conclusion is that - right now - I don't think we really understand how stars form...

5 Dec
TBC
Jamie Bolton (Nottingham)
3.45pm  C23

Star formation is a key problem in astronomy which impacts on galaxy formation and evolution, and sets the initial conditions for planet formation. I will talk about our current understanding of local, low-mass star formation. Firstly, how we think that bound star clusters form from smaller substructure. And also how binary observations suggest that star formation might vary from region to region even though the IMF stays the same. The conclusion is that - right now - I don't think we really understand how stars form...

12 Dec
Searching for stellar IMF variations in extreme environments
Nate Bastian (Liverpool)
3.45pm  C23

TBC

The astronomy group runs a weekly lunchtime talk programme with staff, postdocs, students and visitors giving short talks on a subject of interest to the group. Talks begin at 1pm on Thursdays in room A113 (unless stated otherwise) in the Centre for Astronomy and Particle Theory.

The talks have a duration of approximately 20-30 minutes, and are followed by a short question and answer session.
Click on an event for more information.

Event organiser: Tomáš Šoltinský

Date Speaker Title
##### Abstract

As I haven't done much in the realm of research in galaxies, I thought I'd talk about fun attempts to get rockets to fly around the solar system. This is a cut down, mathed up, version of my public talk on the subject. Featuring no galaxies, no redshifts, no Sersic or other parameters. Does features some rather questionable health and safety decisions though.

The Machine Learning Seminars are a monthly talk on aspects of machine learning in science.

Event organiser: Maggie Lieu

Date Speaker Title
##### Abstract

The image quality including noise, clarity, dynamic range, color and so on, highly depends on the parameter-tuning Image Signal Process (ISP) pipeline in both phone and professional camera, even in the camera of autopilot system. In this, an auto ISP tuning algorithm, which is regarded as an optimization problem, is developed to find the best ISP parameter for image quality. The key point of tuning is to accurately evaluate the low-level image quality. First, an pixel alignment and color-light style transfer based on deep learning is developed to eliminate the difference which is not focused on between the selected golden pictures (usually shot by professional camera devices). Then several neutral network models are trained to evaluate the noise, clarity, dynamic range level difference between the golden pictures and the images. Finally, the hersuic algorithm is used to optimize the best ISP parameters based on that the aforementioned subjective assessment is regarded as the optimization function.

##### Abstract

The ESA Φ-lab aims to accelerate the future of Earth Observation (EO) by operating as a “catalyst” for EO innovative ideas and transformative technologies. AI for Earth Observation (AI4EO) focuses on harnessing the power of Artificial Intelligence (AI) with the vast amount of EO data now available, and it is the Φ-lab initiative to exploit the great potential of AI that is still largely untapped. While today the new boost of AI4EO is mainly related to Computer Vision applied to high-resolution satellite imagery, there are many other areas for Earth Science, prediction and big data analytics that could benefit from AI. In particular, Deep Learning is pushing AI to new levels beyond human performance. This talk will give an overview of the current successes and challenges of AI for Space Applications and present a few methodological use-cases which will lead to impactful applications, from vegetation mapping to cyclone tracking.

Every week, a student or post-doc presents a recent paper that caught his/her attention. Staff are not allowed at these meetings to encourage students to discuss freely. More details can be found on the wiki hosted at PB Works (password required).

The Journal Club takes place every Tuesday, at 1pm in room A113 of the Cripps Building.

Event organiser: Daniel Cornwell

#### Current schedule:

19 October
Dan Cornwell
26 October
Tomáš Šoltinský
02 November
Mick Greener
09 November
Kellie de Vos
23 November
Roan Haggar
30 November
Lizzie Taylor
07 December
Leonardo de Albernaz Ferreira

This Colloquium series hosts prominent scientists who will discuss some of the newest developments in physics and astronomy. It is aimed at a general physics audience at a level accessible to physics PhD students. All Colloquia will be held in Physics building at 4pm followed by refreshments in room C10.
Event Organiser:  Juan P. Garrahan (Condensed-matter theory), Peter Beton (Experimental CM/Nanoscience), Josef Granwehr (Magnetic Resonance), Lucia Hackermuller (Cold Atoms), David Maltby (Astronomy), Tony Padilla (Particle Theory)