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Seeing the whole picture

STAGES has observed the Abell 901/902 supercluster with many of the world's most powerful telescopes, covering wavelengths from the X-ray all the way to the radio.

What do we gain by looking at the same objects in many different ways? The figure below shows just how different galaxies can look when we use telescopes that are sensitive to different types of radiation.  

For example, star formation hidden behind a shroud of dust can be invisible to Hubble but easily apparent to the Spitzer Space Telescope. Likewise, an otherwise dull-looking blob of a galaxy may be resolved into a spectacular merger with the resolution of Hubble.  A supermassive black hole lurking at the centre of a galaxy can be so highly obscurbed that only the most energetic X-ray photos can get through.




Clearly, to see the whole picture and build up a complete census of galaxy properties, we need to observe our galaxies at as many wavelengths as possible.

STAGES multiwavelength coverage

Below we list the facilities used for STAGES, and what we are looking for at each wavelength.  

	Instrument/Survey	scientific contribution
	Hubble Space Telescope: high resolution images at visible wavelengths	galaxy morphologies, sizes, and weak gravitational lensing
	COMBO-17:   ground-based optical images in 17 different filters	photometric redshifts, stellar masses, and galaxy spectral energy distributions (SEDs) for 15000 galaxies
	2dF spectrograph: spectra for 300 cluster galaxies	accurate spectroscopic redshifts;  star formation properties
	XMM-Newton:   X-ray imaging and spectra	mapping of hot intracluster medium; identification of active galactic nuclei
	Spitzer Space Telescope: mid-infrared imaging	identification of dust-obscured star formation and active galactic nuclei
	COMBO-17+4: near-infrared extention to COMBO-17	improved photometric redshifts and stellar mass estimation
	GALEX: near- and far-ultraviolet imaging	identification of active star formation
	GMRT: radio imaging	identification of dust-obscured star formation, radio galaxies
	computer modelling: constrained simulations	models of the dark matter, gas and galaxies help us to understand how the system may have formed