The VLA survey of the Chandra deep fieldysouth. II. Identification and host galaxy properties of submillijansky sources

We present the optical and infrared identifications of the 266 radio sources detected at 20 cm with the Very Large Array in the Chandra Deep Field-South. Using deep i-band Advanced Camera for Surveys, R-band Wide Field Imager, K-band SOFI NTT, K-band ISAAC VLT and Spitzer imaging data, we are able to find reliable counterparts for 254 (similar to 95%) VLA sources. Twelve radio sources remain unidentified, and three of them are "empty fields.'' Using literature and our own data we are able to assign redshifts to 186 (similar to 70%) radio sources: 108 are spectroscopic redshifts and 78 are reliable photometric redshifts. Based on the rest-frame colors and morphological distributions of the host galaxies, we find evidences for a change in the submillijansky radio source population: (1) above approximate to 0.08 mJy early-type galaxies are dominating and (2) at flux densities below approximate to 0.08 mJy, starburst galaxies become dominant.