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OATS-DAUT SEMINAR
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Speaker:
Pavel Kroupa (Argelander-Institut fuer Astronomie (AIfA), Bonn University)
Title:
Are the dSph satellite galaxies tidal-dwarfs?
Date: Wednesday, April 2nd, 2008
Time: 12:00
Venue: Villa Bazzoni
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Abstract:
The Milky Way has about 15 low-mass dwarf-spheroidal (dSph) satellites.
These have luminosities and internal velocity dispersions similar to
globular clusters but are about 100 times larger. The usual
interpretation is that these objects are dark-matter dominated: the
stars are located in the innermost regions of 10-100 times more massive
dark-matter sub-halos. However, many of the dSph satellites are
sub-structured and appear to be distorted. Such distortions are most
readily explained if the satellites are significantly affected by the
Milky Way tide such that dark matter does not significantly shield them.
Furthermore, the satellites are distributed in a relatively thin plane
extending to 250 kpc which is highly inclined to the disk of the Milky
Way. This plane appears to be rotationally supported. This is most
readily explained if the dSph satellites are causally related, i.e. if
they share a common orbital angular momentum vector. All of this can be
understood within a conservative framework, in which early galaxy-galaxy
encounters produce tidal-dwarf galaxies. Applied to the Milky Way this
suggests an early (about 10 Gyr ago) encounter which left a population
of related TDGs in orbit.
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contact: Simone Recchi (OATS)