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Dwarf ellipticals in the eye of SAURON: dynamical & stellar population analysis in 3D

Published online by Cambridge University Press:  09 February 2015

Agnieszka Ryś
Affiliation:
Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain email: [email protected] Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain
Jesús Falcón-Barroso
Affiliation:
Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain email: [email protected] Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain
Glenn van de Ven
Affiliation:
Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
Mina Koleva
Affiliation:
Sterrenkundig Observatorium, Ghent University, Krijgslaan 281, S9, B-9000 Gent, Belgium
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Abstract

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We present the dynamical and stellar population analysis of 12 dwarf elliptical galaxies (dEs) observed using the SAURON IFU (WHT, La Palma). We demonstrate that dEs have lower angular momenta than their presumed late-type progenitors and we show that dE circular velocity curves are steeper than the rotation curves of galaxies with equal and up to an order of magnitude higher luminosity. Transformation due to tidal harassment is able to explain all of the above, unless the dE progenitors were already compact and had lower angular momenta at higher redshifts. We then look at the star formation histories (SFHs) of our galaxies and find that for the majority of them star formation activity was either still strong at a few Gyr of age or they experienced a secondary burst of star formation roughly at that time. This latter possibility would be in agreement with the scenario where tidal harassment drives the remaining gas inwards and induces a secondary star formation episode. Finally, one of our galaxies appears to be composed exclusively of an old population (≳12 Gyr). Combining this with our earlier dynamical results, we conclude that it either was ram-pressure stripped early on in its evolution in a group environment and subsequently tidally heated (which lowered its angular momentum and increased compactness), or that it evolved in situ in the cluster's central parts, compact enough to avoid tidal disruption.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2015 

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