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

Esteban A. Orozco, Eric F. Jiménez-Andrade, Eric J. Murphy, Ian Smail, Emmanuel Momjian, Ian Heywood, Miguel Vega-Gutierrez, Christa DeCoursey

First listed 2025-06-25 | Last updated 2025-06-25

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 $\approx 1 μ$Jy beam$^{-1}$, at the phase center, and sub-arcsec angular resolution ($θ_{1/2}=0.82$ 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 ($μ$), 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$σ$ 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 ($μ\gtrsim 2$) in the VLA Frontier Fields survey, which is adequate to zoom into star formation processes of main sequence galaxies at $z\approx 1-2$.

Short digest

Ultra-deep 6 GHz VLA imaging of Abell 2744 (z=0.307) reaches ≈1 µJy beam−1 at 0.82″, yielding 93 detections, 46 with optical/NIR counterparts spanning z=0.15–3.55 (median z=0.93; median M⋆≈2.3×10^10 M⊙). Radio-inferred SFRs exceed UV–NIR estimates by roughly an order of magnitude, pointing to heavily obscured star formation missed by rest-UV/optical tracers. No individual radio counterparts are found for the z≈6 Little Red Dots; stacking sets a stringent 3σ limit of L6 GHz < 4.1×10^39 erg s−1. The survey also assembles 22 μ≳2 lensed systems, enabling sub-arcsecond probes of main-sequence galaxies at z∼1–2.

Key figures to inspect

• Sensitivity/beam map of the 6 GHz mosaic: verify the ≈1 µJy beam−1 floor at the phase center, the 0.82″ synthesized beam, and how noise rises with radius across Abell 2744.
• Radio–UV/NIR SFR comparison plot: inspect the ≈10× offset, trends with redshift or M⋆, and whether AGN-flagged sources drive outliers.
• LRD stacking analysis: view the postage-stamp stack, radial profile, and flux-density limit that translates to L6 GHz < 4.1×10^39 erg s−1 at z≈6.
• Lens-model/magnification distribution: check μ estimates and spatial locations for the 22 μ≳2 sources relative to the critical curves.
• Postage stamps of representative lensed galaxies: compare 6 GHz contours with HST/NIR images to see alignment, sizes, and any evidence for compact star-forming knots.