  The Center for Adaptive Optics Treasury Survey (CATS) aims to combine deep
HST images in the optical with deep Keck adaptive optics (AO) data in the
near-infrared (NIR) to study distant galaxies, AGN, and supernovae. We recently
achieved an important new milestone by securing the first Keck laser guide star
AO image of faint galaxies. Six galaxies with redshifts ranging from 0.3-1.0
were targeted in one pointing in the GOODS-S field. Two are Chandra Deep Field
South sources, XID-56 and XID-536, with complex morphologies suggestive of
recent merger activity. Substructures seen in the NIR AO image (FWHM ~ 0.1"),
including multiple tight knots in XID-56 and a double nucleus in XID-536, are
confirmed in the optical HST images. These structures are unresolved in the
best seeing-limited (FWHM ~ 0.5") NIR images. Stellar population synthesis
models of the substructures indicate that XID-56 is a gas rich merger with a
recent burst of star formation and significant amounts of dust. XID-536 appears
to be a merger of two evolved stellar populations.
