The VLA Frontier Fields Survey: A 6GHz High-resolution Radio Survey of Abell 2744

TL;DR

This paper presents the deepest 6GHz radio image of galaxy cluster Abell 2744, detecting 93 sources, analyzing their properties, and exploring high-redshift galaxy emission, with implications for star formation and galaxy evolution.

Contribution

It provides the deepest high-resolution 6GHz radio observations of Abell 2744, identifying sources and analyzing their properties, including star formation rates and high-redshift galaxy limits.

Findings

93 sources detected with S/N ≥ 5

Radio SFRs are an order of magnitude higher than UV-IR SFRs

No significant radio detections of z≈6 LRD galaxies

Abstract

We present a 6GHz radio continuum image of the galaxy cluster Abell 2744 ($z = 0.307$) obtained with the Karl G. Jansky Very Large Array (VLA) as part of the VLA Frontier Fields program, whose goal is to explore the radio continuum emission from high-redshift galaxies that are magnified by foreground, massive galaxy clusters. With an rms noise of $\approx 1 \mu$Jy beam$^{-1}$, at the phase center, and sub-arcsec angular resolution ($\theta_{1/2}=0.82$ arcsec), this is the deepest and most detailed radio image of Abell 2744 ever obtained. A total of 93 sources are detected with a peak signal-to-noise ratio $\geq5$, of which 46 have optical/near-infrared (IR) counterparts with available redshift, magnification ($\mu$), and stellar mass (${M}_*$) estimates. The radio sources are distributed over a redshift from 0.15 to 3.55, with a median redshift value of $z = 0.93$, and a median stellar mass of ${M}_{*}= 2.3 \times 10^{10}\,\rm{M}_{\odot}$. A comparison between the radio-based star formation rates (SFRs) and those derived from ultraviolet-to-near IR data reveals that the radio SFRs are, on average, an order of magnitude higher than the ultraviolet-to-near IR SFRs. We look for radio counterparts of the so-called "Little Red Dots (LRDs)'' galaxies at $z\approx6$ in Abell 2744, but find no significant detections. After stacking, we derive a 3$\sigma$ upper limit to the 6GHz radio luminosity of LRDs of $4.1\times 10^{39}\,\rm erg\,s^{-1}$. Finally, we present a sample of 22 moderately/strongly lensed galaxies ($\mu \gtrsim 2$) in the VLA Frontier Fields survey, which is adequate to zoom into star formation processes of main sequence galaxies at $z\approx 1-2$.