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Evolution and luminosity functions of sub-mJy radio sources

Submitter: Colloquium
Description: Speaker: Paolo Padovani (ESO-HQ)

I present the evolutionary properties and luminosity functions of the radio sources belonging to the Chandra Deep Field South VLA survey, which reaches a flux density limit at 1.4 GHz of 42 microJy at the field center and redshift ~ 5. We use an unprecedented classification scheme based on radio, far- and near-IR, optical, and X-ray data to disentangle star-forming galaxies from active galactic nuclei (AGN) and radio-quiet from radio-loud AGN. We strengthen our previous result that star-forming galaxies become dominant only below 0.1 mJy. Radio-quiet AGN are confirmed to be an important class of sub-mJy sources, accounting for ~ 30% of the sample (and ~ 60% of all AGN).

The sub-mJy radio sky turns out to be a complex mix of star-forming galaxies and radio-quiet AGN evolving at a similar, strong rate, non-evolving low-luminosity radio galaxies, and declining radio powerful (P > 3 x 10^24 W/Hz) AGN. Our results suggest that radio emission in radio-quiet AGN is closely related to star formation.

In the plot are shown the number counts of the sub-mJy sources found in the VLA-CDFS observations. The total (black triangles) is split into the number counts for star-forming galaxies (green circles) and AGN (red squares). The latter are again split into radio-loud AGN (purple triangles) and radio-quiet AGN (blue circles).
Copyright: Paolo Padovani
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