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.
Highlights
Dwarf galaxies are by number the most common kind of galaxies in the Local Group
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
By means of N-body numerical simulations, the effects of the tidal forces induced by a host galactic potential on a multicomponent satellite galaxy
Summary
Among all types of dwarf galaxies, such as dwarf irregulars, dwarf ellipticals, transition types, and dwarf spheroidal (dSphs), the latter dominate the satellite population of the large spirals. Dwarf spheroidal galaxies are faint (with luminosities between 103–107L ), metal poor and tend not to be rotationally supported. The star formation histories of these small objects are known to be complex and vary from object to object, but all dSphs contain ancient stellar populations, with ages >10 Gyr old. In most dSphs the ancient stellar component is the dominant one or even the only one present (e.g., Sculptor, Draco, Ursa Minor); there are a few cases where intermediate age stars (3–6 Gyr old) are present (such as Carina) or dominate the overall stellar population (e.g., Fornax, Leo I) [3,4,5]
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