The Very Large Array Survey of the Chandra Deep Field South. IV. Source Population
Abstract
We present a detailed analysis of 256 radio sources from our deep (flux density limit of 42 μJy at the field center at 1.4 GHz) Chandra Deep Field South 1.4 and 5 GHz VLA survey. The radio population is studied by using a wealth of multiwavelength information in the radio, optical, and X-ray bands. The availability of redshifts for ~80% of the sources in our complete sample allows us to derive reliable luminosity estimates for the majority of the objects. X-ray data, including upper limits, for all our sources turn out to be a key factor in establishing the nature of faint radio sources. Due to the faint optical levels probed by this study, we have uncovered a population of distant active galactic nuclei (AGNs) systematically missing from many previous studies of sub-millijansky radio source identifications. We find that, while the well-known flattening of the radio number counts below 1 mJy is mostly due to star-forming galaxies, these sources and AGNs make up an approximately equal fraction of the sub-millijansky sky, contrary to some previous results. The AGNs include radio galaxies, mostly of the low-power, Fanaroff-Riley I type, and a significant radio-quiet component, which amounts to approximately one fifth of the total sample. The ratio of radio-to-optical luminosity depends more on radio luminosity, rather than being due to optical absorption.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2009
- DOI:
- 10.1088/0004-637X/694/1/235
- arXiv:
- arXiv:0812.2997
- Bibcode:
- 2009ApJ...694..235P
- Keywords:
-
- galaxies: active;
- galaxies: starburst;
- radio continuum: galaxies;
- X-rays: galaxies;
- Astrophysics
- E-Print:
- 13 pages, 8 figures, accepted for publication in the Astrophysical Journal