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Advances in Astronomy
Volume 2010, Article ID 194345, 14 pages
http://dx.doi.org/10.1155/2010/194345
Research Article

The Effect of Tidal Stripping on Composite Stellar Populations in Dwarf Spheroidal Galaxies

1Kapteyn Astronomical Institute, P.O. Box 800, 9747 AD Groningen, The Netherlands
2European Organisation for Astronomical Research in the Southern Hemisphere, Karl-Schwarzschild-Stra├če 2, 85740 Garching bei Muenchen, Germany

Received 30 April 2009; Revised 30 August 2009; Accepted 1 October 2009

Academic Editor: Andrey V. Kravtsov

Copyright © 2010 Laura V. Sales et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We use N-body simulations to study the effects of tides on the kinematical structure of satellite galaxies orbiting a Milky Way-like potential. Here we focus on the evolution of a spherical, dark matter dominated satellite, which is modelled with two stellar components set ab initio to be spatially and kinematically segregated, in a way that resembles the configuration of the metal poor and metal rich stellar populations in several dwarf spheroidals of the Local Group. We find that an important attenuation of the initial differences in the distribution of the two stellar components occurs for orbits with small pericentric radii. This is mainly due to (i) the loss of the gravitational support provided by the dark matter component after tidal stripping takes place and (ii) tides preferentially affect the more extended stellar component, leading to a net decrease in its velocity dispersion as a response for the mass loss, which thus shrinks the kinematical gap. We apply these ideas to the Sculptor and Carina dwarf spheroidals. Differences in their orbits might help to explain why in the former a clear kinematical separation between metal poor and metal rich stars is apparent, while in Carina this segregation is significantly more subtle.