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Session 63 - Surveys of Galaxies.
Oral session, Thursday, January 08
Georgetown,
We have recently completed several deep surveys using the VLA at 8 GHz with one sigma sensitivities ranging from 1.5 \muJy to 5 \muJy. These surveys are capable of detecting radio galaxies with luminsoity in excess of the break in the RLF, P_* \sim 10^25 W/Hz, out to z = 10 if they exist and thus are well suited for studying AGN formation and evolution. Follow-up optical work has identified more than 90% of these microjy radio sources, primarily with luminous star-forming galaxies and low-luminosity AGN (--23 < M_B<--21). Suprisingly, these microjy radio sources have approximately the same median redshift (z \sim 0.8) as the 3C identifications, although that sample reached almost one million times less sensitive flux denisty limits.
A few radio sources remain unidentified down to the best optical limits available. In particular, one radio source located in the HDF has no optical counterpart to the detection limit of R \sim 29. We discuss the possibility that this source is a very young AGN, possibly at z > 6, and thus obscured by the Lyman break at optical wavelengths. If our hypothesis is corect, then the host should be detectable in a reasonable integration with NICMOS.
