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

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.