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

TL;DR

This study uses N-body simulations to explore how tidal forces from a Milky Way-like galaxy influence the stellar populations and kinematic structures of dwarf spheroidal galaxies, explaining observed differences in their stellar populations.

Contribution

It demonstrates how tidal stripping affects the distribution and kinematics of stellar populations in dwarf galaxies, providing insights into their observed properties.

Findings

Tidal stripping reduces differences between stellar populations in dwarf galaxies.

Dark matter loss weakens gravitational support, altering stellar distributions.

Orbital parameters influence the degree of kinematic segregation observed.

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. Our work is motivated by observations of dwarf spheroidal galaxies in the Local Group, for which often a distinction is possible between a cold centrally concentrated metal rich and a hot, extended metal poor population. 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 (r_per < 20 kpc). This is mainly due to: i) the loss of the gravitational support provided by the dark matter component after tidal stripping takes place, which forces a re-configuration of the luminous components, 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, under the assumption of similar initial configurations, 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.