Stellar populations in tidally stirred dwarf galaxies

TL;DR

This study uses N-body simulations to explore how stellar populations in dwarf galaxies evolve under tidal forces, showing that multiple populations can persist and change over billions of years.

Contribution

It demonstrates that the tidal stirring scenario can naturally produce and maintain multiple stellar populations in dwarf spheroidal galaxies.

Findings

Outer stars migrate inward forming an extended core

Inner stars develop outer tails over time

Outer populations are more tidally stripped

Abstract

Using N-body simulations we study the evolution of separate stellar populations in dwarf galaxies in the context of the tidal stirring scenario for the formation of dwarf spheroidal (dSph) galaxies in the Local Group. The dwarf galaxies, initially composed of a stellar disk and a dark matter halo, are placed on seven different orbits around the Milky Way. The stars are divided into two populations, within and outside the half-light radius, and their positions are followed for 10 Gyr. We find that the populations retain different density distributions even over such long timescales. Some of the stars of the outer population migrate to the central part of the dwarf forming an extended core while the stars of the inner population develop a tail in the outer parts. In addition, the outer population is more heavily stripped by tidal forces from the Milky Way and may become subdominant at all radii on tight enough orbits. We conclude that the tidal stirring model is fully compatible with the presence of multiple stellar populations in dSph galaxies.