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

Abstract

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 active galactic nucleus (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 per cent) as galaxies whose radio emission is dominated by star-formation activity, 6/24 (25 per cent) as intermediate star-forming galaxies, and 6/24 (25 per cent) 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 \gt $ 1.5.