The Red Sequence of High-Redshift Clusters: a Comparison with Cosmological Galaxy Formation Models

TL;DR

This study compares semi-analytic galaxy formation models with observations of high-redshift galaxy clusters, revealing that models predict a well-defined red sequence at z=1.2 with properties similar to observations, highlighting the evolution of galaxy populations.

Contribution

The paper provides a detailed comparison between semi-analytic models and spectro-photometric observations of distant galaxy clusters, focusing on the properties and evolution of the red sequence at high redshift.

Findings

A well-defined, narrow red sequence exists at z=1.2 in models.

Cluster red sequence is more populated than the field at the same redshift.

Model predictions are generally consistent with observations, with some differences in scatter values.

Abstract

We compare the results from a semi-analytic model of galaxy formation with spectro-photometric observations of distant galaxy clusters observed in the range 0.8< z< 1.3. We investigate the properties of their red sequence (RS) galaxies and compare them with those of the field at the same redshift. In our model we find that i) a well-defined, narrow RS is obtained already by z= 1.2; this is found to be more populated than the field RS, analogously to what observed and predicted at z=0; ii) the predicted U-V rest-frame colors and scatter of the cluster RS at z=1.2 have average values of 1 and 0.15 respectively, with a cluster-to-cluster variance of 0.2 and 0.06, respectively. The scatter of the RS of cluster galaxies is around 5 times smaller than the corresponding field value; iii) when the RS galaxies are considered, the mass growth histories of field and cluster galaxies at z=1.2 are similar, with 90 % of the stellar mass of RS galaxies at z=1.2 already formed at cosmic times t=2.5 Gyr, and 50 % at t=1 Gyr; v) the predicted distribution of stellar ages of RS galaxies at z=1.2 peaks at 3.7 Gyr for both cluster and field populations; however, for the latter the distribution is significantly skewed toward lower ages. When compared with observations, the above findings show an overall consistency, although the average value 0.07 of the observed cluster RS scatter (U-V colors) at z=1.2 is smaller than the corresponding model central value. We discuss the physical origin and the significance of the above results in the framework of cosmological galaxy formation.