Mid - infrared Identification of 6 cm Radio Source Counterparts in the Extended Groth Strip

A new 6 cm survey of almost 0.6 deg to a limit of 0.55 mJy/beam (10σ) finds 37 isolated radio sources and 7 radio source pairs (not necessarily physical companions). IRAC counterparts are identified for at least 92% of the radio sources within the area of deep IRAC coverage, which includes 31 isolated sources and 6 pairs. This contrasts with an identification rate of <74% to R < 23.95 in visible light. Eight of the IRAC galaxies have power law spectral energy distributions, implying that the mid-infrared emission comes from a powerful AGN. The remaining 26 IRAC galaxies show stellar emission in the mid-infrared, probably in most of these galaxies because the stellar emission is bright enough to outshine an underlying AGN. The infrared colors suggest that the majority of these galaxies are bulge-dominated and have redshifts 0.5 . z . 1. Visible Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 Department of Astronomy, University of California, Berkeley, CA 94720–3411 Hubble Fellow, Steward Observatory, University of Arizona, Tucson, AZ 85721 National Radio Astronomy Observatory, P.O. Box 0, 1003 Lopezville Road, Socorro, NM 87801 Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ UK Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ UK UCO/Lick Observatory, Dept. of Astronomy & Astrophysics, Univ. of California, Santa Cruz, CA 95064 Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tuscon, AZ 85721 Subaru Telescope, National Astronomical Observatory of Japan, 650 North A’ohoku Place, Hilo, HI 96720