A Fully Identified Sample of AEGIS20 Microjansky Radio Sources

Infrared 3.6-8 μm images of the Extended Groth Strip yield plausible counterpart identifications for all but one of 510 radio sources in the AEGIS20 S(1.4 GHz) > 50 μJy sample. This is the first such deep sample that has been effectively 100% identified. Achieving the same identification rate at R band would require observations reaching R _AB > 27. Spectroscopic redshifts are available for 46% of the sample and photometric redshifts for an additional 47%. Almost all of the sources with 3.6 μm AB magnitudes brighter than 19 have spectroscopic redshifts z < 1.1, while fainter objects predominantly have photometric redshifts with 1 <~ z <~ 3. Unlike more powerful radio sources that are hosted by galaxies having large stellar masses within a relatively narrow range, the AEGIS20 counterparts have stellar masses spanning more than a factor of 10 at z ~ 1. The sources are roughly 10%-15% starbursts at z <~ 0.5 and 20%-25% active galactic nuclei mostly at z > 1 with the remainder of uncertain nature.