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S. V. W. Beckwith (STScI), H.-W. Rix (MPIA, Heidelberg), C. Peng (Steward Observatory), D. McIntosh (UMass), J. Caldwell (STScI), K. Meisenheimer (MPIA), C. Wolf (Oxford), L Wisotzki (AIP, Potsdam), A. Borch, B. Haeussler (MPIA), M. Barden (MPE and MPIA), GEMS Collaboration
We are presenting first results from the large HST program GEMS, with which we are determining the evolution of galaxy structure over the last half of cosmic history from galaxy images in the redshift range from 0.1 to 1.2.
We have obtained a large, two-color (V and z) ACS image mosaic over an area of 30'x30', encompassing the Chandra Deep Field South and GOODS field. From the ground-based survey COMBO-17 we have obtained 10,000 galaxy and AGN redshifts to m(R)~24 in this area, with spectral energy distributions (SED) from 3500AA to 9000AA for each object. We are in the process of obtaining from the HST images structural parameters, such as disk sizes and bulge-to-disk ratios, and stellar masses for all these galaxies.
This unique data set will let us to resolve some of the most important issues in galaxy evolution. We can see directly why star formation activity has declined dramatically since z~1: changes in the interaction and merger rate, waning fuel supply, or simply a shift of star-formation to progressively less massive systems. By resolving all galaxies in rest-frame B, we can separate the bulges, bars, and disks to determine if the bulges simply dim, while disks grow radially with time. The growing disk surface mass density might increase the incidence of large-scale bars at lower redshifts.
We will report on the status of the project and show first results on early type and star-bursting galaxies.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.