The sub-mJy radio population of the E-CDFS: optical and infrared counterpart identification

TL;DR

This study presents a comprehensive multi-wavelength catalog of 883 deep radio sources in the E-CDFS, identifying optical/IR counterparts, redshifts, and X-ray properties to facilitate future galaxy population research.

Contribution

It introduces a new, deep multi-wavelength catalog with high counterpart identification accuracy and redshift assignment for faint radio sources.

Findings

95% of radio sources have reliable counterparts

74% detected optically, 21% only in IR

81% assigned redshifts, including 37% spectroscopic

Abstract

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.