SuperCLASS -- II: Photometric Redshifts and Characteristics of Spatially-Resolved $\mu$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${}_{1.4}>75$ $\mu$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 $\alpha =0.59\pm 0.04$. 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 $>7\sigma$ in the density map and we confirm the photometric redshifts are consistent with previously measured spectra from a few galaxies at the cluster centers.

arXiv comment14 pages, 13 figures, accepted for publication in MNRAS on March 3 2020

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• SuperCLASS -- I. The Super CLuster Assisted Shear Survey: Project overview and Data Release 1
• Intrinsic alignments of the extended radio continuum emission of galaxies in the EAGLE simulations