A SAURON study of dwarf elliptical galaxies in the Virgo Cluster: kinematics and stellar populations

TL;DR

This study uses integral field spectroscopy to analyze the kinematics and stellar populations of four dwarf elliptical galaxies in the Virgo Cluster, revealing their diverse properties and potential evolutionary links to larger ellipticals.

Contribution

It provides detailed two-dimensional kinematic and stellar population data for Virgo dwarf ellipticals, highlighting their structural diversity and challenging simple formation models.

Findings

Detection of substructures and varying flattening in dEs.

Identification of non-rotating, flattened dEs suggesting triaxial shapes.

dEs follow similar mass trends as giant ellipticals but differ in abundance ratios.

Abstract

Dwarf elliptical galaxies (dEs) are the most common galaxy type in nearby galaxy clusters; even so, many of their basic properties have yet to be quantified. Here we present the results of our study of 4 Virgo dwarf ellipticals obtained with the SAURON integral field unit on the William Herschel Telescope (La Palma, Spain). While traditional long-slit observations are likely to miss more complicated kinematic features, with SAURON we are able to study both kinematics and stellar populations in two dimensions, obtaining a much more detailed view of the mass distribution and star formation histories. What is visible even in such a small sample is that dEs are not a uniform group, not only morphologically, but also as far as their kinematic and stellar population properties are concerned. We find the presence of substructures, varying degrees of flattening and of rotation, as well as differences in age and metallicity gradients. We confirm that two of our galaxies are significantly flattened, yet non-rotating objects, which makes them likely triaxial systems. The comparison between the dwarf and the giant groups shows that dEs could be a low-mass extension of Es in the sense that they do seem to follow the same trends with mass. However, dEs as progenitors of Es seem less likely as we have seen that dEs have much lower abundance ratios.