Galaxies spatially coincident with the JKCS041 X-ray emission display a red sequence at z~2.2

TL;DR

This study identifies a red galaxy sequence associated with the X-ray emission of cluster JKCS041, estimating its redshift at approximately 2.2 through color analysis, indicating a distant galaxy cluster.

Contribution

The paper presents the first detection of a red sequence at z~2.2 coincident with X-ray emission, providing a new method for estimating high-redshift cluster distances.

Findings

Red sequence at z~2.2 coincident with X-ray emission

Red sequence is 0.32 mag redder than at z=1.62

Estimated redshift of JKCS041 is 2.20±0.11

Abstract

New deep z'-J data readly show a narrow red sequence co-centered with, and similary concentrated to, the extended X-ray emission of the cluster of galaxies JKCS041. The JKCS041 red sequence is 0.32+/-0.06 mag redder in z'-J than the red sequence of the zspec=1.62 IRC0218A cluster, putting JKCS041 at z<<1.62. The colour difference of the two red sequences gives a red-sequence based redshift of z=2.20+/-0.11 for JKCS041, where the uncertainty accounts for uncertainties in stellar synthesis population models, in photometric calibration and in the red sequence colour of both JKCS041 and IRC0218A clusters.