The sub-mJy radio population of the E-CDFS: optical and infrared
  counterpart identification
  We study a sample of 883 sources detected in a deep Very Large Array survey
at 1.4 GHz in the Extended Chandra Deep Field South. The paper focuses on the
identification of their optical and infrared (IR) counterparts. We use a
likelihood ratio technique that is particularly useful when dealing with deep
optical images to minimize the number of spurious associations. We find a
reliable counterpart for 95% of our radio sources. Most of the counterparts
(74%) are detected at optical wavelengths, but there is a significant fraction
(21%) only detectable in the IR. Combining newly acquired optical spectra with
data from the literature we are able to assign a redshift to 81% of the
identified radio sources (37% spectroscopic). We also investigate the X-ray
properties of the radio sources using the Chandra 4 Ms and 250 ks observations.
In particular, we use a stacking technique to derive the average properties of
radio objects undetected in the Chandra images. The results of our analysis are
collected in a new catalog containing the position of the optical/IR
counterpart, the redshift information and the X-ray fluxes. It is the deepest
multi-wavelength catalog of radio sources, which will be used for future study
of this galaxy population.
