GEMS , G alaxy E volution from M orphologies and S EDs , is a large-area ( 800 arcmin ^ { 2 } ) two-color ( F606W and F850LP ) imaging survey with the Advanced Camera for Surveys on HST .
Centered on the Chandra Deep Field South , it covers an area of \sim 28 ^ { \prime } \times 28 ^ { \prime } , or about 120 Hubble Deep Field areas , to a depth of m _ { AB } ( F606W ) = 28.3 ( 5 \sigma ) and m _ { AB } ( F850LP ) = 27.1 ( 5 \sigma ) for compact sources .
In its central \sim 1 / 4 , GEMS incorporates ACS imaging from the GOODS project .
Focusing on the redshift range 0.2 \mathrel { \raise 1.29 pt \hbox { $ < $ } \mkern - 14.0 mu \lower 2.58 pt \hbox { $ \sim$ } } z% \mathrel { \raise 1.29 pt \hbox { $ < $ } \mkern - 14.0 mu \lower 2.58 pt \hbox { $ \sim$ } } 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 AGN .
This paper provides an overview of the science goals , the experiment design , the data reduction and the science analysis plan for GEMS .