Deep silence: radio properties of little red dots

TL;DR

This study examined the radio properties of 919 high-redshift 'little red dots' and found no detectable radio emission, indicating these sources likely lack significant radio-loud active galactic nuclei.

Contribution

The paper provides the first comprehensive radio analysis of LRDs, using stacking techniques to set upper limits on their radio emission and suggesting they host weak or no radio AGNs.

Findings

No radio counterparts detected in VLASS and FIRST surveys.

Stacking analyses show no radio emission above noise levels.

LRDs likely do not host strong radio-loud AGNs.

Abstract

To investigate the radio properties of the recently found high-redshift population, we collected a sample of $919$ little red dots (LRDs) from the literature. By cross-matching their coordinates with the radio catalogues based on the first- and second-epoch observations of the Very Large Array Sky Survey (VLASS) and the Faint Images of the Radio Sky at Twenty-centimeters (FIRST) survey, we found no radio counterparts coinciding with any of the LRDs. To uncover possible sub-mJy level weak radio emission, we performed mean and median image stacking analyses of empty-field 'Quick Look' VLASS and FIRST image cutouts centred on the LRD positions. We found no radio emission above $3\sigma$ noise levels ($\sim11$ and $\sim18~\mu$Jy~beam$^{-1}$ for the VLASS and FIRST maps, respectively) in either of the stacked images for the LRD sample, while the noise levels of the single-epoch images are comparable to those found earlier in the stacking of high-redshift radio-quiet active galactic nuclei (AGNs). The non-detection of radio emission in LRDs suggests these sources host weaker (or no) radio AGNs.