PEARLS: JWST counterparts of micro-Jy radio sources in the Time Domain Field

TL;DR

This study uses JWST/NIRCam data to identify and analyze the properties of radio sources in the Time Domain Field, revealing their redshifts, host galaxy characteristics, and the nature of their radio emission, with implications for extragalactic science.

Contribution

First detailed JWST/NIRCam analysis of micro-Jy radio sources in the TDF, linking radio emission to galaxy properties and AGN activity with high-resolution imaging.

Findings

62 of 63 radio sources have identified counterparts

Radio emission mainly from star formation (~2/3) and AGN (~1/3)

High accuracy in counterpart identification reduces misidentification risks

Abstract

The Time Domain Field (TDF) near the North Ecliptic Pole in JWST's continuous-viewing zone will become a premier "blank field" for extragalactic science. JWST/NIRCam data in a 16 arcmin$^2$ portion of the TDF identify 4.4 $\mu$m counterparts for 62 of 63 3 GHz sources with S(3 GHz) > 5 {\mu}Jy. The one unidentified radio source may be a lobe of a nearby Seyfert galaxy, or it may be an infrared-faint radio source. The bulk properties of the radio-host galaxies are consistent with those found by previous work: redshifts range from 0.14 to 4.4 with a median redshift of 1.33. The radio emission arises primarily from star formation in $\sim 2/3$ of the sample and from an active galactic nucleus in $\sim 1/3$, but just over half the sample shows evidence for an AGN either in the spectral energy distribution or by radio excess. All but three counterparts are brighter than magnitude 23 AB at 4.4 $\mu$m, and the exquisite resolution of JWST identifies correct counterparts for sources for which observations with lower angular resolution would mis-identify a nearby bright source as the counterpart when the correct one is faint and red. Up to 11% of counterparts might have been unidentified or misidentified absent NIRCam observations.