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Something Bright at the Edge of Everything: A Uniquely JWST-Dark Radio Source in COSMOS

Mingyu Li

Abstract

For decades, astronomers have been searching for bright radio sources deep into the epoch of reionization (EoR). The most distant, powerful radio sources are expected to reside in heavily dust-obscured galaxies, exceedingly faint at optical and infrared wavelengths. Motivated by this, I systematically cross-match radio and JWST source catalogs in the COSMOS field and identify a uniquely JWST-dark radio source: the only object undetected in every JWST band, yet clearly detected in radio data from LOFAR 144 MHz to the VLA 3 GHz. The source is only marginally resolved and shows a steep, unbroken radio spectrum, while remaining undetected in all available HST, JWST, Chandra, Herschel, and ALMA imaging. It may represent an extremely dust-obscured radio-loud source at cosmic dawn, or alternatively a detached radio lobe whose host galaxy lies elsewhere. In either case, it highlights the new discovery space at the intersection of deep radio surveys and JWST imaging.

Something Bright at the Edge of Everything: A Uniquely JWST-Dark Radio Source in COSMOS

Abstract

For decades, astronomers have been searching for bright radio sources deep into the epoch of reionization (EoR). The most distant, powerful radio sources are expected to reside in heavily dust-obscured galaxies, exceedingly faint at optical and infrared wavelengths. Motivated by this, I systematically cross-match radio and JWST source catalogs in the COSMOS field and identify a uniquely JWST-dark radio source: the only object undetected in every JWST band, yet clearly detected in radio data from LOFAR 144 MHz to the VLA 3 GHz. The source is only marginally resolved and shows a steep, unbroken radio spectrum, while remaining undetected in all available HST, JWST, Chandra, Herschel, and ALMA imaging. It may represent an extremely dust-obscured radio-loud source at cosmic dawn, or alternatively a detached radio lobe whose host galaxy lies elsewhere. In either case, it highlights the new discovery space at the intersection of deep radio surveys and JWST imaging.

Paper Structure

This paper contains 3 sections, 1 figure.

Table of Contents

  1. Introduction
  2. A JWST-Dark Radio Source
  3. Discussion

Figures (1)

  • Figure 1: Multi-wavelength observations of the JWST-dark radio source. Top Left: JWST NIRCam color image (blue: F090W+F115W+F150W; green: F200W+F277W; red: F356W+F410M+F444W) with VLA 3 GHz contours overlaid at $5,15, 25\sigma$ in yellow, where $\sigma=2.3~\mu$Jy beam$^{-1}$. Top Middle: the stacked HST ACS (F475W+F606W+F814W) image, JWST MIRI image (F770W+F1280W+F1500W+F1800W+F2100W), and radio imaging data from 144 MHz to 3 GHz with dashed circles indicating the corresponding beam size. Top Right: radio spectral fit, yielding $\alpha=-0.99\pm0.03$ for $S_\nu\propto\nu^\alpha$. Bottom: Photometric measurements and spectral energy distribution. Gray shadows show the $3\sigma$ upper limits from HST, JWST, Herschel, and ALMA, together with the radio detections denoted by black diamonds. Blue circles and lines represent a model SED of a heavily obscured radio-loud AGN Endsley2023MNRAS.520.4609E at $z\sim7$ for comparison.