Properties of Polarized Radio Sources in the Wide Chandra Deep Field South from 2 to 4GHz

TL;DR

This study analyzes the polarization properties of radio sources in the Wide Chandra Deep Field South at 2-4 GHz, revealing fractional polarization levels, Faraday rotation measures, and correlations with spectral index, aiding future large-scale surveys.

Contribution

It provides the first detailed polarization characterization of sources in the W-CDFS at S-band, including fractional polarization, rotation measures, and their relation to spectral properties.

Findings

Sources >10mJy have ~3% fractional polarization.

Estimated <3% fractional polarization for sources <1mJy.

Faraday rotation consistent with Milky Way contribution.

Abstract

We present a study of the linear polarization properties of radio sources within the 10 deg$^2$ Wide Chandra Deep Field South (W-CDFS) in S-band (2-4 GHz). Our W-CDFS image has an angular resolution of 15 arcsec and a 1$\sigma$ RMS in Stokes $I$ of $\approx$50 $\mu$Jy/beam. We detect 1920 distinct source components in Stokes $I$ and 175 in linear polarization. We examine the polarized source counts, Faraday Rotation measures, and fractional polarization of the sources in the survey. We show that sources with a total intensity above $\approx$10mJy have a mean fractional polarization value of $\approx$3% from modeling the polarized counts. We also calculate an estimate for the limit on the fractional polarization level of sources with a total intensity below 1mJy (mostly star-forming galaxies) of $\stackrel{<}{_{\sim}}$3% using stacking. The mean Faraday Rotation we measure is consistent with that due to the Milky Way. We also show that fractional polarization is correlated with in-band spectral index, consistent with a lower mean fractional polarization for the flat-spectrum population. In addition to characterizing the S-band polarization properties of sources in the W-CDFS, this study will be used to validate the shallower, but higher angular resolution S-band polarimetric information that the VLA Sky Survey will provide for the whole sky above Declination -40 degrees over the next few years.