MeerKAT observations of starburst galaxies and AGNs within the core of XMMXCS J2215.9-1738 at $z$ = 1.46

TL;DR

This study uses MeerKAT radio observations combined with optical and infrared data to analyze star formation and AGN activity in a high-redshift galaxy cluster, revealing significant star formation and AGN presence at $z$=1.46.

Contribution

First detailed radio analysis of XMMXCS J2215.9-1738 at $z$=1.46, classifying galaxy activity and estimating star formation rates within the cluster core.

Findings

50% of cluster galaxies are star-formation dominated

Estimated total star formation rate of 1700 solar masses per year

High AGN fraction consistent with other high-redshift clusters

Abstract

We present the first detailed radio study of the galaxy cluster XMMXCS J2215.9-1738 at $z$ = 1.46 using MeerKAT $L$-band (1.3 GHz) observations. We combine our radio observation with archival optical and infrared data to investigate the star formation and AGN population within $R_{200}$ ($R = $ 0.8 Mpc) of the cluster centre. Using three selection criteria; the radio luminosity, the far-infrared radio ratio ($q_{\rm{IR}}$) and the mid-infrared colour, we distinguish galaxies with radio emission predominantly powered by star formation from that powered by AGNs. We selected 24 cluster members within $R_{\rm{200}}$ in the MeerKAT image based on either their photometric or spectroscopic redshift. We classified 12/24 ($50\%$) as galaxies whose radio emission is dominated by star-formation activity, 6/24 ($25\%$) as intermediate star-forming galaxies and 6/24 ($25\%$) as AGN-dominated galaxies. Using the radio continuum luminosities of the star-forming cluster galaxies, we estimated an integrated star formation rate (SFR) value of 1700 $\pm$ 330 M$_{\odot}$yr$^{-1}$ within $R_{200}$. We derived a mass-normalized integrated SFR value of $(570 \pm 110) \times 10^{-14}$ yr$^{-1}$. This supports previous observational and theoretical studies that indicated a rapid increase in star formation activity within the core of high-redshift clusters. We also show that the high AGN fraction within the cluster core is consistent with previous cluster observations at $z >$ 1.5.