A JWST Paschen-alpha Calibration of the Radio Luminosity-Star Formation Rate Relation at z~1.3

TL;DR

This study calibrates the relation between radio luminosity and star formation rate at z~1.3 using JWST Paschen-alpha data, confirming the relation's consistency with local universe findings and exploring synchrotron emission delays.

Contribution

It provides a new calibration of the radio luminosity-SFR relation at intermediate redshift using JWST Paschen-alpha data, extending previous local universe relations.

Findings

Radio luminosity correlates with SFR at z~1.3 consistent with local relations.

Stacking undetected sources yields a significant radio detection.

Synchrotron emission delay of ~10-75 Myr explains scatter in the correlation.

Abstract

As radio emission from normal galaxies is a dust-free tracer of star formation, tracing the star formation history of the Universe is a key goal of the SKA and ngVLA. In order to investigate how well radio luminosity traces star formation rate (SFR) in the early Universe, we have examined the radio properties of a JWST Paschen-alpha sample of galaxies at 1.0<=z<=1.8. In the GOODS-S field, we cross-matched a sample of 506 FRESCO Paschen-alpha emitters with the 1.23 GHz radio continuum data from the MeerKAT MIGHTEE survey finding 47 detections. After filtering for AGN (via X-ray detections, hot mid-infrared dust and extended radio emission), as well as blended sources, we obtained a sample of SFGs comprising: 11 cataloged radio detections, 18 non-cataloged detections (at ~3-5sigma) and 298 undetected sources. Stacking the 298 undetected sources we obtain a 3.3sigma detection in the radio. This sample, along with a local sample of Paschen-alpha emitters, lies along previous radio luminosity/SFR relations from local (z<0.2) to high redshift (z~1). Fitting the FRESCO data at 1.0<=z<=1.8 we find log(L_1.4GHz) = (1.31+/-0.17) x log(SFR_Pa-alpha) + (21.36+/-0.17) which is consistent with other literature relations. We can explain some of the observed scatter in the L_1.4GHz/SFR_Pa-alpha correlation by a toy model in which the synchrotron emission is a delayed/averaged tracer of the instantaneous Paschen-alpha SFR by ~10/75 Myr.