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

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. 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 [α/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 time‐scales, and in the transformation of discy dwarfs to more spheroidal objects by harassment over longer time‐scales. This points towards a continuing infalling scenario for the evolution of dEs.

Formation and evolution of dwarf early-type galaxies in the Virgo cluster

“…Notes. (Υ * I ) is only indicative, the large errors in the stellar populations (Michielsen et al 2008) make the uncertainties of (Υ * I ) of the same order of magnitude as the values. the galaxies.…”

“…This might happen through interactions with the intergalactic medium (IGM), such as ram-pressure stripping (Boselli et al 2008a,b), galaxy-galaxy interactions (e.g., Byrd & Valtonen 1990), and galaxy harassment (e.g., Moore et al 1998;Mastropietro et al 2005). It has been shown that all these interactions are able to reproduce some of the observational properties of local dEs in clusters, such as their structural parameters (Lisker et al 2006b(Lisker et al , 2007 or their stellar populations (Geha et al 2002(Geha et al , 2003van Zee et al 2004b;Michielsen et al 2008;Paudel et al 2010), but none of them have been tested against the kinematic properties. In this regard, whereas in the harassment scenario the system is rapidly heated, leading to an increase in the velocity dispersion of the galaxy and a decrease in its rotation (Mastropietro et al 2005), the angular momentum is conserved in a ram-pressure stripping event (Boselli et al 2008a,b).…”

“…Later on, it was shown that dEs were no longer small Es with simple, old, and metal-poor stellar populations, but much more complex objects exhibiting a wide range of stellar contents. For example, in the Virgo cluster, they have stellar populations ranging from very young (around 1 Gyr old) luminosity-weighted ages to as old as the oldest Es galaxies (14 Gyr) (Michielsen et al 2008). Their proximity allowed detailed studies of their structural properties that indicated that, behind their elliptical appearance, dEs show a wide variety of underlying structures, like disks, spiral arms, irregular features, etc, making them a very heterogeneous class of galaxies (Lisker et al 2006a(Lisker et al ,b, 2007.…”

The Next Generation Virgo Cluster Survey Xvi: The Angular Momentum of Dwarf Early-Type Galaxies From Globular Cluster Satellites

“…Regarding their stellar populations, they span a wide range of subsolar metallicities, from [M/H]∼−0.1 to −1.5, and old ages, from 1 to 14 Gyr (Michielsen et al 2008;Paudel et al 2010;Koleva et al 2011;Toloba et al 2014a).…”

Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models

“…However, it is worth noting that the base models have been successfully applied to these galaxies. In fact it is possible to obtain a good proxy for the [Mg/Fe] abundance, if appropriate indices are employed for the analysis Sánchez-Blázquez et al 2006b;Yamada et al 2006;de la Rosa et al 2007;Michielsen et al 2008;Vazdekis et al 2010;La Barbera et al 2013). This proxy leads to a linear relation with the abundance ratio estimated with the aid of models that specifically take into account such non-solar element mixtures (e.g., Tantalo et al 1998;Thomas et al 2003; Lee & Worthey 2005;Graves & Schiavon 2008).…”