# Galaxy and Mass Assembly (GAMA): Probing the merger histories of massive galaxies via stellar populations

## TL;DR

This study investigates how the stellar populations of satellite galaxies in close pairs with massive primaries vary with environment, revealing age and metallicity differences linked to galaxy and halo mass.

## Contribution

It provides new insights into galaxy merger histories by analyzing stellar populations in satellite galaxies across different environments and mass scales.

## Key findings

- Satellites around more massive galaxies are older and possibly more metal-rich.
- Age differences of about 1-2 Gyr are observed in lower-mass satellites.
- Population trends are consistent with old stellar ages in the outer regions of massive galaxies.

## Abstract

The merging history of galaxies can be traced with studies of dynamically close pairs. These consist of a massive primary galaxy and a less massive secondary (or satellite) galaxy. The study of the stellar populations of secondary (lower mass) galaxies in close pairs provides a way to understand galaxy growth by mergers. Here we focus on systems involving at least one massive galaxy - with stellar mass above $10^{11}M_\odot$ in the highly complete GAMA survey. Our working sample comprises 2,692 satellite galaxy spectra (0.1<z<0.3). These spectra are combined into high S/N stacks, and binned according to both an "internal" parameter, the stellar mass of the satellite galaxy (i.e. the secondary), and an "external" parameter, selecting either the mass of the primary in the pair, or the mass of the corresponding dark matter halo. We find significant variations in the age of the populations with respect to environment. At fixed mass, satellites around the most massive galaxies are older and possibly more metal rich, with age differences ~1-2Gyr within the subset of lower mass satellites ($\sim 10^{10}M_\odot$). These variations are similar when stacking with respect to the halo mass of the group where the pair is embedded. The population trends in the lower-mass satellites are consistent with the old stellar ages found in the outer regions of massive galaxies.