Morphological evolution of cluster red sequence galaxies in the past 9 Gyr

Abstract

Galaxies arrive on the red sequences of clusters at high redshift (z > 1) once their star formation is quenched and evolve passively thereafter. However, we have previously found that cluster red sequence galaxies (CRSGs) undergo significant morphological evolution subsequent to the cessation of star formation, at some point in the past 9-10 Gyr. Through a detailed study of a large sample of cluster red sequence galaxies spanning 0.2 < z < 1.4 we elucidate the details of this evolution. Below z ∼ 0.5 − 0.6 (in the last 5-6 Gyr) there is little or no morphological evolution in the population as a whole, unlike in the previous 4-5 Gyrs. Over this earlier time (i) disklike systems with Sérsic n < 2 progressively disappear, as (ii) the range of their axial ratios similarly decreases, removing the most elongated systems (those consistent with thin disks seen at an appreciable inclination angle), and (iii) radial colour gradients (bluer outwards) decrease in an absolute sense from significant age-related gradients to a residual level consistent with the metallicity-induced gradients seen in low redshift cluster members. The distribution of their effective radii shows some evidence of evolution, consistent with growth of at most a factor < 1.5 between z ∼ 1.4 and z ∼ 0.5, significantly less than for comparable field galaxies, while the distribution of their central (< 1kpc) bulge surface densities shows no evolution at least at z < 1. A simple model involving the fading and thickening of a disk component after comparatively recent quenching (after z ∼ 1.5) around an otherwise passively evolving older spheroid component is consistent with all of these findings.

Colour gradients in cluster ellipticals at z ∼ 1.4: the hidden content of the galaxy central regions

“…This is not surprising since colour gradients trace principally the variation of the stellar component dominating the galaxy within 1-2Re while the other properties are derived considering the whole galaxy mass. Similar results are also found by De Propris et al (2015Propris et al ( , 2016 for cluster red sequence galaxies at a comparable redshift and by Gargiulo et al (2012) for a sample of field early-type galaxies at 0.9 < z < 1.92. We have also verified if the amplitude of the colour gradients depends on the position of the galaxy inside the cluster, namely on the radial distance from the cluster centre (i.e.…”

“…To reproduce the colour gradients locally observed, the presence of both age and metallicity gradient is needed. It is a conclusion also reached by De Propris et al (2015Propris et al ( , 2016 in cluster early-type galaxies at z > 1, where age gradients were associated with the presence of disc-like morphologies.…”

The rise and fall of the UV upturn: z = 0.3, 0.55, and 0.7

“…As in our previous work, we use the red sequence to select quiescent cluster members in all clusters. This has already been shown to be an efficient method to identify early-type galaxies in clusters, with a high degree of fidelity (e.g., see Rozo et al 2015;De Propris et al 2016). Galaxies belonging to these tight red sequences appear to show no evidence of current or recent star formation, even in high redshift clusters at z > 1 (e.g., Mei et al 2006).…”

The KMOS Cluster Survey (KCS). II. The Effect of Environment on the Structural Properties of Massive Cluster Galaxies at Redshift 1.39 < z < 1.61*

“…Trujillo et al 2011) and is difficult to reconcile with the fact that these galaxies may have steep age gradients (e.g. De Propris et al 2015Propris et al , 2016Chan et al 2016). Dry minor mergers, on the other hand, have been shown to be able to explain most of the abovementioned observed properties (see e.g.…”