Environmental Effects on Satellite Galaxies: The Link Between Concentration, Size and Colour Profile

TL;DR

This study analyzes how environment influences satellite galaxy properties, revealing that satellite galaxies exhibit smaller sizes, higher concentrations, and redder colors than centrals of similar stellar mass, explained by a simple fading star formation model.

Contribution

It demonstrates that environmental effects on satellite galaxies can be explained by star formation fading without invoking strong morphological transformations.

Findings

Late-type satellites are smaller and more concentrated than centrals.

Satellite galaxies are redder and have lower surface brightness.

Differences are explained by a 2-3 Gyr star formation decline model.

Abstract

Using the SDSS DR4 group catalogue of Yang et al. (2007), we investigate sizes, concentrations, colour gradients and surface brightness profiles of central and satellite galaxies. We compare central and satellite galaxies at fixed stellar mass, in order to disentangle environmental from stellar mass dependencies. Early and late type galaxies are defined according to concentration. We find that at fixed stellar mass, late type satellite galaxies have smaller radii and larger concentrations than late type central galaxies. No such differences are found for early-type galaxies. We have also constructed surface brightness and colour profiles for the central and satellite galaxies in our sample. We find that late-type satellite galaxies have a lower surface brightness and redder colours than late-type central galaxies. We show that all observed differences between satellite and central galaxies can be explained by a simple fading model, in which the star formation in the disk decreases over timescales of 2-3 Gyr after a galaxy becomes a satellite. Processes that induce strong morphological changes (e.g. harassment) and processes that strip the galaxy of its entire ISM need not to be invoked in order to explain the environmental dependencies we find.