Galaxy Clusters in the IRAC Dark Field I: Growth of the red sequence

TL;DR

This study investigates the evolution of galaxy clusters at z~1 by analyzing the growth of their red sequence, revealing that massive galaxies evolve faster than less massive ones, with less massive galaxies still actively forming stars.

Contribution

First measurement of red sequence growth in galaxy clusters at z~1 using deep infrared and optical data, highlighting differential galaxy evolution based on mass.

Findings

Fewer faint galaxies on the red sequence at z~1 compared to local clusters.

More massive galaxies have already evolved onto the red sequence.

Less massive galaxies are still forming stars and have not yet settled onto the red sequence.

Abstract

Using three newly identified galaxy clusters at z~1 (photometric redshift) we measure the evolution of the galaxies within clusters from high redshift to the present day by studying the growth of the red cluster sequence. The clusters are located in the Spitzer Infrared Array Camera (IRAC) Dark Field, an extremely deep mid-infrared survey near the north ecliptic pole with photometry in 18 total bands from X-ray through far-IR. Two of the candidate clusters are additionally detected as extended emission in matching Chandra data in the survey area allowing us to measure their masses to be M_{500}= 6.2 \pm 1.0 \times 10^{13} and 3.6 \pm 1.1 \times 10^{13} solar masses. For all three clusters we create a composite color magnitude diagram in rest-frame B-K using our deep HST and Spitzer imaging. By comparing the fraction of low luminosity member galaxies on the composite red sequence with the corresponding population in local clusters at z=0.1 taken from the COSMOS survey, we examine the effect of a galaxy's mass on its evolution. We find a deficit of faint galaxies on the red sequence in our z~1 clusters which implies that more massive galaxies have evolved in clusters faster than less massive galaxies, and that the less massive galaxies are still forming stars in clusters such that they have not yet settled onto the red sequence.