The astronomy group welcomes applications from postgraduates who wish to carry out research leading to the award of a Ph.D.

Applications are made using the online application form found here after registering a username and password. Further information on the admissions procedure is available from either the postgraduate admissions tutor, Prof. Juan P. Garrahan, or the astronomy admissions coordinator, Dr. James Bolton.

Interviews for our STFC funded positions (for UK/EU students who meet the appropriate eligibility requirements) are normally held during the period from late February to early March each year. We therefore strongly encourage the submission of applications before January 31.

Overseas students may also be eligible for one of our international research scholarships, and should ensure their online application is submitted at least six weeks before the closing date for these schemes.

Examples of typical Ph.D. projects offered by the astronomy group may be found by following the research projects link on the right of this page. Further details regarding postgraduate funding opportunities are available at the links listed below, and more general information about being a postgraduate in the School of Physics and Astronomy may be obtained on our postgraduate study page.

1. Flickering black holes in the distant Universe

Omar Almaini, Michael Merrifield

Quasars are the most luminous objects in the Universe, powered by accretion onto supermassive black holes. A key characteristic of quasars is their extreme variability, which provides a means of identifying these rare objects (given data of sufficient quality). The aim of this project is to identify quasars in a unique patch of sky (the Ultra Deep Survey), using very deep infrared imaging taken over an unprecedented baseline of 10 years. This would be the first study of its kind, which will provide a new and entirely independent census of quasar activity in the distant Universe. We expect to identify several thousand new quasars, allowing us to measure the growth of black holes at early times. By probing physical scales that are unresolvable by other means, the light curves will also provide new tests for models of quasar fuelling and accretion. As a bonus, we will also identify supernovae among the ~250,000 normal galaxies in the field, to provide a new statistical study of the prevalence of supernova activity in distant galaxies.

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2. Understanding galaxy transformation

Omar Almaini, David Maltby

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 galaxies 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. The aim of this project is to understand and unravel these key transformative processes. The project will involve a combination of deep imaging data from the Ultra-Deep Survey (the deepest infrared survey over ~1 sq degree, led by Nottingham) and unique deep spectroscopy from the VLT VANDELS project. Imaging will provide the morphological characteristics, while the spectra will allow us to understand the internal physical processes. Many unanswered questions remain. Are distant galaxies quenched by feedback from accreting black holes or massive stellar outflows? Is the morphological transformation related to the quenching of star formation? Do galaxy mergers play a role? By combining information obtained from multi-wavelength imaging and spectroscopy, the aim of this project is to solve these important problems, to finally understand the processes driving the evolution of distant galaxies.

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3. Galaxy evolution and environment

Alfonso Aragon-Salamanca

The morphology, star-formation history, dynamics, and many other properties of galaxies depend strongly on where they formed and where they live. In other words, galaxies are affected by their environment. If we want to have a full understanding of how galaxies form and evolve, it is crucial to study all the physical mechanisms that influence their evolution. Using a combination of HST and new state-of-the-art ground-based observations of galaxies in clusters, groups, filaments and low-density regions we will study how the environment affects and/or determines the properties of galaxies, and how these change with time. In doing so, we will be able to learn what physical mechanisms are responsible for the changes that galaxies experience throughout their lives.

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4. Exploring the epoch of reionisation with simulations of the cosmic web

James Bolton

The intergalactic medium forms the link between galaxy formation and cosmology; its spatial distribution is sometimes referred to as the cosmic web due to the filamentary network which intergalactic gas and dark matter traces on large scales. The first stars and galaxies to form in this web-like distribution of matter - when the Universe was only a fraction of its current age - produced the ultra-violet radiation and heavy elements which photo-ionised and chemically enriched the cold, neutral intergalactic gas. Observing the impact of this so-called reionisation era on the cosmic web therefore provides an indirect probe of the formation and evolution of these first galaxies. In the next decade, there will be a significant amount of emphasis placed on exploring this exciting new observational frontier. Detailed models of reionisation and the intergalactic medium will therefore provide an indispensible tool for interpreting forthcoming data sets and understanding the astrophysics of the early Universe. This project will use the state-of-the-art Sherwood simulation suite (www.nottingham.ac.uk/astronomy/sherwood/) to investigate the impact of intergalactic structure on the epoch of reionisation, and to explore the observational signatures expected in the spectra of the most distant quasars and galaxies yet discovered.

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5. Searching for the shadows of proto-clusters in the early Universe

James Bolton, Nina Hatch, Frazer Pearce

Galaxy proto-clusters are the distant progenitors of local galaxy clusters. At redshift z>2 they are large, diffuse structures, consisting of many dark matter haloes. Observations of these galaxy proto-clusters provide some of the most direct tests of galaxy and cluster formation. They are excellent laboratories in which to study feedback from supermassive black holes, and the formation of the most massive galaxies in the Universe. However, detecting these objects in the first place is a huge challenge. This project will investigate a new method to locate and study proto-clusters utilising the vast quantities of hydrogen gas within these large structures. This hydrogen gas is traced by absorption lines in the Lyman-alpha forest -- the series of hydrogen absorption lines observable in the spectra of distant quasars. These absorption lines provide a unique window into the physical properties of proto-clusters in the early Universe. This project will use observations of Lyman-alpha absorption lines in quasar spectra to detect the cool intra-protocluster gas at high redshift. State-of-the-art hydrodynamical simulations (www.nottingham.ac.uk/astronomy/sherwood/) will be used in combination with the observational data to determine the properties of proto-clusters, and to further develop techniques suitable for blind searches for proto-clusters using quasar survey data. The precise balance of observation and theory may be adjusted depending on the interests of the student

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6. The evolution of dark matter in the Universe

Chris Conselice

We currently do not understand the nature of dark matter, yet we can detect it in great abundance in the nearby universe where it makes up 90% of all mass. What we would like to understand is how dark matter has evolved through cosmic time. This will reveal not only how dark matter itself was assembled in the universe, which we know very little about, but also how dark matter is related to the process of galaxy formation.

To address this our group has recently obtained spectroscopy of distant galaxies when the universe was only a few Gyr old with the VLT using the SINFONI instrument. This data will provide internal kinematics for these young galaxies, which in turn will reveal their internal dynamics from which not only early kinematic properties can be measured, but also their total dark matter content. By comparing the dark matter to stellar masses with galaxies at a variety of distances, we will be able to determine how dark matter has assembled with galaxies. This is furthermore a major test of the CDM paradigm for understanding how galaxies and the universe assembled.

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7. Satellites Galaxies and Halo Light Surrounding Massive Galaxies

Chris Conselice

Massive galaxies are the brightest systems in the universe, and thus the easiest to study. They are also the type of galaxies where we have the most theoretical models on their formation, yet observationally we still do not know how they and their dark matter halos formed. While we know a great deal about massive galaxies, some of their unexplored features include their outer diffuse regions, and their satellite galaxies, neither of which have been studied in any detail. Diffuse light around massive galaxies have longer dynamical time-scales than denser regions, and thus allow us to probe the history of galaxy formation, in particular how it relates to their satellite galaxies, which merge with the central to build up their masses. The problem is that it is very difficult to study these galaxies and regions, as they are very faint and have a low surface brightness.

The Dark Energy Survey (DES) on the Blanco 4m telescope at Cerro-Tololo Observatory in Chile will cover 5000 square degrees of the sky, and is an ideal data set to investigate these related questions. The student on this project will led the effort towards finding the faintest satellite galaxies, as well as investigate the faint outer parts of galaxies which have not yet been explored. The project will involve collaborating with the DES team, including observational trips to Chile, and leading other follow up individual projects on various telescopes. The result of this will be a better understanding of how satellite and central galaxies have formed in the universe.

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8. The First Galaxies with the James Webb Space Telescope (JWST)

Chris Conselice

The James Webb space telescope will launch at the end of 2017, providing a revolution in our understanding of the first galaxies within the first 500 Million years after the Big Bang. This update to the Hubble Space Telescope will allow us to probe the very first galaxies in a way that we are unable to do today. Nottingham is part of the team with guaranteed early data from JWST. The student hired for this project will at first lead some preparatory work using data we are acquiring with the Very Large Telescope (VLT) in Chile to determine the best targets for JWST. After launch the student will then take on a leadership role in investigating the stellar populations, ages, structure and star formation rates of the first galaxies. This will ultimately be interpreted in terms of theories of galaxies formation to test and exclude different ideas for how the first generations of galaxies and star formed.

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9. A new era in gravitational lensing

Simon Dye

Strong gravitational lensing is now recognised as one of the most powerful methods for measuring the amount and distribution of dark matter and baryonic mass in galaxies. Such measurements are key for the understanding of galaxy formation and evolution but there are presently only around 150 strong galaxy lens systems known and most of these are at low redshifts where the pace of galaxy evolution has significantly slowed. This situation is expected to improve dramatically in the near future with new higher redshift lens samples containing tens of thousands of lenses resulting from two forthcoming facilities: The Large Synoptic Survey Telescope which comes online in 2019 and the Euclid satellite due for launch in 2020. Our group has developed a technique that has now become the 'industry standard' for modelling strong lenses but the method is too labour intensive for scaling up to the large datasets anticipated. This project is therefore concerned with tackling this challenge directly by developing methods for the automatic detection and modelling of strong lens systems in large survey data.

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10. Measuring dark matter in galaxies using gravitational lensing

Simon Dye

Our group plays a key role in the gravitational lensing element of the Herschel-ATLAS survey carried out by the Herschel Space Observatory. H-ATLAS is currently uncovering 100’s of new strong lenses which are presently being followed up by the brand-new ALMA telescope in Chile. The new dataset is offering great improvements over current lens samples by virtue of its exquisite resolution and higher redshift range. This allows astronomers to probe deeper into the earlier Universe when galaxy evolution was in its early stages. The project being offered is to carry out lens modelling of the ALMA observations to learn about both the foreground galaxy doing the lensing and the background galaxy being lensed.

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11. Galaxy clusters in the Dark Energy Survey

Meghan Gray

The Dark Energy Survey (DES) is an ongoing, five year optical survey aiming to understand the nature of Dark Energy. One product of these observations will be a catalogue of ~400 000 galaxy clusters. The mass function of these clusters is useful for cosmological purposes, but the multiwavelength observations of such a large sample of clusters also provides an immense resource for understanding the mass assembly of the largest structures in the Universe and the nature of the galaxies living inside them. This project will involve close collaboration with members of the DES Cluster Working Group to study cluster masses, distributions, and galaxy populations. We will also make use of follow-up observations including ongoing spectroscopic surveys to understand the dynamical states of the clusters and surrounding large-scale structure.

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12. Galaxy clusters: bridging theory and observation

Meghan Gray, Frazer Pearce

Most galaxies in the Universe live in groups or clusters, making such large-scale structure critical both for studies of cosmology and of galaxy evolution. This project builds on a successful research program working at the interface between simulations (Pearce) and observations (Gray) to understand the physical processes that influence these objects and the galaxies inhabiting them. Students will exploit state-of-the-art N-body and hydrodynamic simulations, galaxy evolution models, and large imaging and spectrographic surveys to study the properties of large scale structure in both the real and mock universes. Comparison of both approaches allows us to simultaneously test the model physics, gain insight into the data, and understand the ultimate limitations of our measurements. Our goals include understanding group and cluster assembly (and implications for large cosmological surveys) as well as distentangling the interplay between galaxy properties and their environments.

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13. Witnessing galaxy formation in the most distant galaxy clusters

Nina Hatch

Galaxy clusters are the densest places a galaxy can live, containing thousands of individual galaxies bound together by their mutual gravitational attraction. Cluster galaxies typically differ in colour and shape from galaxies that reside in the less dense field implying that galaxies are influenced by their environment. Some of these differences are caused by the dense environment acting on the galaxies today, but there are also subtle differences that must have been set long ago. For example, cluster galaxies are typically more massive, older and larger than field galaxies, implying that a galaxy’s surroundings during its birth also have an important and lasting influence. Determining the environment of a galaxy in the early Universe is extremely challenging, so we currently know very little about the role of environment during a galaxy’s birth. This has resulted in a large gap in our understanding of how the Universe evolved. In this Ph.D. project you will use state-of-the-art observations of the most distant galaxy clusters in the Universe to understand how galaxies are influenced by their surroundings whilst they are forming.

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14. Simulating protoclusters

Nina Hatch, Frazer Pearce

In our Universe structure forms hierarchically, with small objects merging to make larger ones. The end state of this process are the largest bound structures in the Universe, giant clusters of thousands of galaxies. These enormous objects are used as the testing ground for theories of galaxy formation and evolution because of their highly complex environment and long history. In this project we aim to catch these giants prior to and in the process of formation, using deep observations to identify galaxies which will eventually form galaxy clusters by the present day. This will allow is to answer such questions as how important a large dark matter halo is to the physics of galaxy transformation and what is the connection between large scale environment and local galaxy formation. To do this we will couple the latest generation of large astrophysical simulations of the Universe to our ongoing deep observation programme, using insights obtained from the full evolutionary history contained within the simulations to shed light on our observational data. We require a student with interests both in high performance computing and large observational programmes.

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15. Galaxies with MaNGA

Michael Merrifield, Alfonso Aragon-Salamanca

It is now quite well established that the distinct components of galaxies -- primarily their bulges and disks -- have different stories to tell about the evolution of these systems. To study these components separately in order to learn how they formed, we need detailed spectral mapping across the entire face of each galaxy, which can now be obtained using integral field unit (IFU) spectrographs. The World-leading project to do this is the Mapping Nearby Galaxies at APO (MaNGA) programme, which is one of the components of the on-going Sloan Digital Sky Survey. MaNGA will produce a huge IFU spectral data set for 10,000 galaxies, allowing their kinematics and chemical properties to be studied in unprecedented detail. As members of this elite programme, we have complete access to all the data, and at this stage in the project we can play a key role in shaping the over-all science programme. PhD students involved in this project will have the opportunity to work with data of a quantity and quality that has never been obtained before, and will interact with the leading scientists in this field from all over the World, to establish their own longer-term research careers.

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16. The stellar phase density of the Universe

Michael Merrifield

Galaxies are fundamentally six-dimensional objects, in that each star is described not only by its position in space but also the components of its velocity in all three directions. Any study of galaxy evolution has to account for all six of these components, not just the projection of them that gives the spatial distribution of starlight. This project involves studying the properties of this full six-dimensional phase space, and using some elementary mixing theory to discover which evolutionary pathways are available to galaxies, and which otherwise-plausible possibilities are ruled out.

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17. Mock skies for large surveys

Frazer Pearce

Computer generated mock observations underpin the interpretation of modern astrophysics. Ongoing and future large survey programmes such as the Dark Energy Survey, Euclid and PanStarrs rely upon such models to train and validate their search algorithms and data extraction techniques. In Nottingham we lead the Mocking Astrophysics project (www.mockingastrophysics.org) which aims to provide verified model skies to these large programmes. Mocking Astrophysics has projects ranging across the entire spectrum of mock catalogue production, from comparing initial conditions generators through Tier-0 production simulation on the world's largest supercomputers to detailed analysis and mock galaxy catalogue production and mock observation using current observational software pipelines. We are looking for a computationally literate student to join of international project team which is gearing up for the launch of the Euclid satellite in 2020.

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