Three candidate clusters around high redshift radio-loud sources: MG1 J04426+0202, 3C 068.2, MS 1426.9+1052

TL;DR

This study identifies significant galaxy overdensities around three high-redshift radio-loud sources, suggesting early cluster formation with red sequences consistent with old stellar populations.

Contribution

It provides near-infrared observations revealing candidate proto-clusters around high-redshift radio sources and analyzes their color-magnitude relations for galaxy formation insights.

Findings

Significant galaxy overdensities up to 19-sigma detected.

Candidate clusters show emerging red sequences.

Red sequence galaxies are consistent with old stellar populations (z_f > 5).

Abstract

We present near-infrared observations of the environments around three radio-loud sources (MG1 J0442+0202, 3C 068.2, and MS 1426.9+1052) at redshifts z=1.10,1.57, and 1.83 (respectively), that are surrounded by near-infrared galaxy overdensities. Overdensities with respect to field counts were found to be significant up to 19-sigma, with twelve times the expected number of galaxies within the inner regions of the densest proto-cluster. Color-magnitude relations are constructed in K_s, J-K_s, with each candidate cluster exhibiting a feature consistent with the beginnings of a red sequence. Galaxy models based on the redshift of the radio source are used to compare expected color-magnitude relations for a given formation epoch with the observed red sequence of each candidate, and are found to be consistent with an old (z_f > 5) formation epoch for a few bright, red galaxies on the red sequence.