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Galaxy Evolution From Morphology And SEDs

GEMS in a Nutshell:

  • largest contiguous field ever imaged with HST (900 arcmin2)
  • mosaic of 9x9 Advanced Camera for Surveys (ACS) pointings
  • Field: Extended Chandra Deep Field South (E-CDFS)
  • Filters: V (F606W) and z (F850LP)
  • 10000 redshifts from COMBO-17 (galaxies down to R<24) in the range: 0.2<z<1.2
  • SEDs from COMBO-17 in the range 3500 to 9250 Ångstroms

GEMS tile #58

(clicking on the red boxes displays the full-resolution version of that region; a larger (334kb) version of the total frame is available by clicking here)

Simulation of a galaxy merger

Galaxy Merger
(animations are available by clicking on the image)

GEMS tile layout

Science Questions:

  • Why has star formation activity declined so dramatically sinze z~1:
    • changes in interaction and merger rate?
    • waning fuel supply?
    • shift of star-formation to progressively less massive systems?
  • How did galactic discs and bulges form and evolve with time?
    • simple dimming of bulges?
    • radial growth of discs?
    • evolution of bars
  • How did AGN host galaxies evolve over the last 10Gyrs?

Comparison of COMBO-17 and GEMS data

GEMS-COMBO animation
(for a larger version (330kb) click on the image)

GEMS has imaged an area of 900 square minutes of arc on the sky with the Advanced Camera for Surveys (ACS) on-board Hubble Space telescope. This contiguous field centred on the Chandra Deep Field South contains roughly 10000 galaxies down to a depth of 24th magnitude in the R-band. The central part was  observed by the GOODS-project to an even fainter flux-limit, while GEMS mainly concentrates on the outer regions, the extended Chandra Deep Field South. For those 10000 objects redshifts in the range 0.2<z<1.2 were determined in the COMBO-17 project, by means of low-resolution spectra using 17 medium band filters. Those spectra not only provide redshifts but also spectral energy distributions (SEDs) from 3500 to 9250 Ångstroms. The mosaic of 9 by 9 ACS pointings in the F606W and F850LP filters will allow us in combination with the known redshifts to construct a rest-frame B-band image of all target galaxies with resolutions < 0.1 arcseconds, corresponding to < 500 parsec in the object's rest-frame. This unique data set including SED and high resolution morphological information will let us determine the evolution of galaxy structure over the last half of cosmic history.