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K. I. Kellermann, E. B. Fomalont (NRAO), P. Rosati, P. Shaver (ESO), CDFS Collaboration
We have used the NRAO VLA to study the radio counterparts of X- ray sources found in the Chandra Deep Field South (Giacconi et al. Astro-ph 007240). The VLA observations were made at 1.4 and 5 GHz with integration times of 12 hours and 16 hours respectively. We detected 20 radio sources within the approximately 16 x 16 arcminute CDFS above a limiting flux density of 200 and 135 microJy at 1.4 and 5 GHz respectively. Eight of the VLA sources have an X-ray counterpart including a peculiar system of interacting galaxies at z=0.07.
Previous deep surveys made at the VLA, Westerbork, and at the Australia Telescope have detected a population of microjansky radio sources which appears to be mostly a mixture of star forming galaxies and AGN. Some ten to fifteen percent of microjansky radio sources are optically faint but are often bright in the infrared and at submm wavelengths. The radio, optical, infrared, and X-ray data suggests that active star formation and AGN heat a surrounding dust cloud.
Further VLA observations are planned which will increase the total number of radio sources to several hundred, comparable with the number of X-ray sources expected after completion of the 1 Megasecond Chandra integration of this field. The combination of extensive radio, infrared and optical material in the CDFS should help to better understand the interaction between star forming activity and AGN at early epochs in the universe.
The VLA is a facility of the NRAO which is operated by Associated Universities, Inc. under cooperative agreement with the NSF.