The relation between stellar populations, structure and environment for dwarf elliptical galaxies from the MAGPOP-ITP

TL;DR

This study analyzes 24 dwarf elliptical galaxies in the Virgo Cluster and field, revealing how their stellar populations, structure, and environment influence their evolution, with implications for galaxy formation theories.

Contribution

It provides new insights into the environmental effects on dwarf elliptical galaxy evolution using optical spectroscopy and correlates stellar populations with galaxy structure and environment.

Findings

Dwarf ellipticals are younger and more metal-poor than normal ellipticals.

Environment influences star formation termination via ram pressure stripping.

Dwarf ellipticals show correlations between age, asymmetry, and Virgocentric distance.

Abstract

Dwarf galaxies, as the most numerous type of galaxy, offer the potential to study galaxy formation and evolution in detail in the nearby Universe. Although they seem to be simple systems at first view, they remain poorly understood. In an attempt to alleviate this situation, the MAGPOP EU Research and Training Network embarked on a study of dwarf galaxies named MAGPOP-ITP (Peletier et al., 2007). In this paper, we present the analysis of a sample of 24 dwarf elliptical galaxies (dEs) in the Virgo Cluster and in the field, using optical long-slit spectroscopy. We examine their stellar populations in combination with their light distribution and environment. We confirm and strengthen previous results that dEs are, on average, younger and more metal-poor than normal elliptical galaxies, and that their [alpha/Fe] abundance ratios scatter around solar. This is in accordance with the downsizing picture of galaxy formation where mass is the main driver for the star formation history. We also find new correlations between the luminosity-weighted mean age, the large-scale asymmetry, and the projected Virgocentric distance. We find that environment plays an important role in the termination of the star formation activity by ram pressure stripping of the gas in short timescales, and in the transformation of disky dwarfs to more spheroidal objects by harassment over longer timescales. This points towards a continuing infall scenario for the evolution of dEs.