SuperCLASS -- II: Photometric Redshifts and Characteristics of Spatially-Resolved $\hat{I}¼$Jy Radio Sources

Abstract

We present optical and near-infrared imaging covering a $\sim$1.53 deg${}^2$ region in the Super-Cluster Assisted Shear Survey (SuperCLASS) field, which aims to make the first robust weak lensing measurement at radio wavelengths. We derive photometric redshifts for $\approx$176,000 sources down to $i_{\mathrm{AB}}^{\prime }\sim 24$ and present photometric redshifts for 1.4 GHz $e$-MERLIN and VLA detected radio sources found in the central 0.26 deg${}^2$. We compile an initial catalog of 149 radio sources brighter than S${}_{1.4}>75$ $\hat{I}¼$Jy and find their photometric redshifts span $0<z_{\mathrm{phot}}<4$ with radio luminosities between $10^{21}-10^{25}$ W Hz${}^{-1}$, with medians of $⟨z⟩=0.55$ and $⟨L_{1.4}⟩=1.9\times 10^{23}$ W Hz${}^{-1}$ respectively. We find 95% of the \uJy\ radio source sample (141/149) have SEDs best fit by star-forming templates while 5% (8/149) are better fit by AGN. Spectral indices are calculated for sources with radio observations from VLA and GMRT at 325 MHz, with an average spectral slope of $\hat{I}\pm =0.59\pm 0.04$. Using the full photometric redshift catalog we construct a density map at the redshift of the known galaxy clusters, $z=0.20\pm 0.08$. Four of the five clusters are prominently detected at $>7\ddot{I}ƒ$ in the density map and we confirm the photometric redshifts are consistent with previously measured spectra from a few galaxies at the cluster centers.

14 pages, 13 figures, accepted for publication in MNRAS on March 3 2020