Late growth of early-type galaxies in low-z massive clusters

We study a sample of 936 early-type galaxies (ETGs) located in 48 low-z regular galaxy clusters with M-200 >= 10(14) M-circle dot at z < 0.1. We examine variations in the concentration index, radius, and colour gradient of ETGs as a function of their stellar mass and loci in the projected phase space (PPS) of the clusters. We aim to understand the environmental influence on the growth of ETGs according to the time since infall into their host clusters. Our analysis indicates a significant change in the behaviour of the concentration index C and colour gradient around M-* approximate to 2 x 10(11) <(M)over tilde>(*). Objects less massive than (M) over tilde (*) present a slight growth of C with M-*, with negative and approximately constant colour gradients in all regions of the PPS. Objects more massive than (M) over tilde (*) present a slight decrease of C with M-*, with colour gradients becoming less negative and approaching zero. We also find that objects more massive than (M) over tilde (*), in all PPS regions, have smaller R-90 for a given R-50, suggesting a smaller external growth in these objects or even a shrinkage possibly due to tidal stripping. Finally, we estimate different dark matter fractions for galaxies in different regions of the PPS, with the ancient satellites having the largest fractions, f(DM) approximate to 65 per cent. These results favour a scenario where cluster ETGs experience environmental influence the longer they remain and the deeper into the gravitational potential they lie, indicating a combination of tidal stripping + harassment, which predominate during infall, followed by mergers + feedback effects affecting the late growth of ancient satellites and BCGs.

Automated summary

We examine the variation in concentration index, radius, and color gradient of 936 early-type galaxies (ETGs) in 48 low-z regular galaxy clusters. Our analysis reveals that the behavior of concentration index and color gradient changes significantly for ETGs with stellar mass around 2x10^11 M. Objects with lower mass showed slight growth in concentration index and constant color gradients, while objects with higher mass showed slight decrease in concentration index and less negative color gradients. In addition, we found that objects with higher mass have smaller R-90 for a given R-50, indicating smaller external growth or even shrinkage possibly due to tidal stripping. Ancient satellites were found to have the highest dark matter fractions, approximately 65%.