Virgo Cluster and field dwarf ellipticals in 3D: I. On the variety of stellar kinematic and line-strength properties

TL;DR

This study provides detailed 3D stellar kinematic and line-strength maps for dwarf elliptical galaxies, revealing high diversity in their properties and suggesting stochastic formation processes influenced by environmental effects.

Contribution

First large-scale integral-field kinematic and line-strength mapping of dwarf ellipticals in different environments, highlighting their diverse properties and implications for galaxy formation theories.

Findings

No direct correlation between rotation and flattening.

Detection of kinematic twists and decoupled components.

Varied line-strength gradients indicating diverse stellar populations.

Abstract

We present the first large-scale stellar kinematic and line-strength maps for dwarf elliptical galaxies (9 in the Virgo Cluster and 3 in the field environment) obtained with the SAURON integral-field unit. No two galaxies in our sample are alike: we see that the level of rotation is not tied to flattening (we have, e.g. round rotators and flattened nonrotators); we observe kinematic twists in 1 Virgo and 1 field object; we discover large-scale kinematically-decoupled components in 2 field galaxies; we see varying gradients in line-strength maps, from nearly flat to strongly peaked in the center. The great variety of morphological, kinematic, and stellar population parameters seen in our data points to a formation scenario in which properties are shaped stochastically. A combined effect of ram-pressure stripping and galaxy harassment is the most probable explanation. We show the need for a comprehensive analysis of kinematic, dynamical, and stellar population properties which will enable us to place dwarf ellipticals and processes that govern their evolution in the wider context of galaxy formation.