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Symposium 241

Abstract details

The Many Faces of Early-Type Dwarfs - Different Snapshots of Their Evolution?
T. Lisker, E.K. Grebel, B. Binggeli

We present a study of several hundred early-type dwarf galaxies (dEs) in the Virgo Cluster with SDSS multicolour imaging, complemented by SDSS spectroscopy and near-infrared photometry for part of the sample. Our results reveal a variety of dE subclasses with systematic differences in stellar content, shape, and clustering properties. Two dozen dEs have blue cores due to ongoing central star formation, yet are dominated by an old stellar population. 41 dEs have disks with bars or spiral arms - but the spirals are not formed by a young stellar population. These two dE populations are not yet virialized and might have emerged recently from a transformation process like galaxy harassment. But even among those dEs without star formation or disks, further subdivisions appear - and only the ones with a compact nucleus appear to follow the classical picture of a dwarf elliptical galaxy. Are all these dE populations just multiple snapshots of the same evolutionary path, or is there more than one way to make dEs? To address this question, we attempt to integrate our observational results about their stellar content and morphological properties into a consistent picture for the long-standing question of dE formation.

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