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A. M. Koekemoer, E. J. Schreier, N. A. Grogin (STScI), R. Giacconi (AUI/JHU), R. Gilli, L. Kewley, C. Norman (JHU), G. Hasinger (AIP), P. Rosati (ESO), A. Marconi, M. Salvati (Arcetri), P. Tozzi (Trieste)
We present recent results from HST/WFPC2 imaging in the V and I bands of three fields within the 1 Msec Chandra Deep Field South (CDFS). HST's unparallelled resolution and sensitivity are sufficient to reveal optical counterparts for 38 of the 42 X-ray sources detected in the 1 Msec CDFS X-ray catalog, and the images reveal the morphologies of most of these objects. We find that the X-ray sources comprise two apparently distinct populations in the optical regime: one optically faint (I ~ 24 - 26) withV-I colors consistent with the I > 24 field population; the other significantly brighter (I < 23) with colors redder than the I < 23 field population. More than 2/3 of the X-ray source counterparts are clearly resolved by HST, while the rest are likely dominated by emission from Type 1 AGN. The optically resolved sources in the brighter population have a very narrow range of V-I color and comprise a mix of both late and early type morphologies at moderate redshifts (z ~ 0.3 - 1). We show that the second population, with fainter optical counterparts, can be explained as being predominantly higher redshift (z ~ 2 - 3) Type 2 AGN.