GEMS: Galaxy Evolution from Morphologies and SEDs

GEMS (Galaxy Evolution from Morphologies and SEDs) is a large-area (800 arcmin2) two-color (F606W and F850LP) imaging survey with the Advanced Camera for Surveys on the Hubble Space Telescope. Centered on the Chandra Deep Field-South, it covers an area of ~28′ × 28′, or about 120 Hubble Deep Field areas, to a depth of mAB(F606W) = 28.3(5 σ) and mAB(F850LP) = 27.1(5 σ) for compact sources. In its central ~1/4, GEMS incorporates ACS imaging from the GOODS project. Focusing on the redshift range 0.2 ≲ z ≲ 1.1, GEMS provides morphologies and structural parameters for nearly 10,000 galaxies where redshift estimates, luminosities, and SEDs exist from COMBO-17. At the same time, GEMS contains detectable host galaxy images for several hundred faint active galactic nuclei. This paper provides an overview of the science goals, the experiment design, the data reduction, and the science analysis plan for GEMS.