Characterizing the satellites of massive galaxies up to z~2: young populations to build the outskirts of nearby massive galaxies

TL;DR

This study examines the properties of satellite galaxies around massive hosts up to redshift 2, revealing their younger ages and bluer colors at lower redshifts, supporting their role in galaxy size evolution.

Contribution

It provides new insights into the stellar ages and colors of satellites over cosmic time, linking satellite accretion to the growth of galaxy outskirts.

Findings

Satellites are bluer than their host galaxies.

Satellites are younger by ~1.5 Gyr at lower redshifts.

Results support satellites' role in building galaxy outskirts.

Abstract

The accretion of minor satellites is currently proposed as the most likely mechanism to explain the significant size evolution of the massive galaxies during the last ~10 Gyr. In this paper we investigate the rest-frame colors and the average stellar ages of satellites found around massive galaxies (Mstar 10^11Msun) since z~2. We find that the satellites have bluer colors than their central galaxies. When exploring the stellar ages of the galaxies, we find that the satellites have similar ages to the massive galaxies that host them at high redshifts, while at lower redshifts they are, on average, ~1.5 Gyr younger. If our satellite galaxies create the envelope of nearby massive galaxies, our results would be compatible with the idea that the outskirts of those galaxies are slightly younger, metal-poorer and with lower [alpha/Fe] abundance ratios than their inner regions.