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OATS-DAUT SEMINAR
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Speaker: Giuseppina Battaglia (ESO, Garching, D)

Title: Chemistry and kinematics of stars in Milky Way dwarf spheroidal galaxies

Date: Tuesday, November 25th, 2008
Time: 12:00
Venue: Villa Bazzoni

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Abstract:
Dwarf spheroidal galaxies (dSphs) are faint, small systems, which can be studied in great detail, on a star-by-star basis, in the vicinity of the Milky Way. The relevance of these objects is manifold, both from a cosmological and galaxy formation/evolution point of view. dSphs appear to be the smallest systems requiring presence of dark matter, and may even be the most dark matter dominated ones. This makes them good testing grounds for predictions of different dark matter models. Their simplicity with respect to larger galaxies offers a great opportunity to learn about the physical processes around star formation and chemical enrichment. Furthermore, current theories of hierarchical structure formation predict that small galaxies are the building blocks of larger ones. Therefore a detailed study of individual stars in these nearby systems is an important step to understand and model the contribution of small galaxies to the assembly of larger galaxies.
As part of the DART project we have carried out detailed studies of a sample of Milky Way dSphs in order to improve our understanding of the properties of these small stellar systems. We have used the ESO/2.2m Wide Field Imager to obtain large area photometry and FLAMES at the VLT to obtain intermediate resolution spectra in the CaII triplet region for hundreds of individual stars out to the nominal tidal radii of these objects.
In this talk I will give an overview of the DART photometric and spectroscopic survey of the Sculptor and Fornax dSphs. I will show that the metallicity and kinematic properties of these systems are quite complex, with the presence of multiple stellar populations, and in Sculptor even of statistically significant rotation. I will then focus on results from the kinematic modelling of Sculptor, aimed to derive the mass content of this object and test predictions from dark matter models. I will show that modelling of the different kinematics and spatial distribution of the multiple stellar populations allows a more accurate determination of the mass of Sculptor with respect to other methods commonly used.
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contact: Andrea Biviano (OATS)