Summary

Sagittarius (Sgr) dwarf spheroidal (dSph) is one of the most massive satellite galaxies of the Milky Way and is the closest to the Galactic center. The ongoing destruction of Sgr dSph produces immense tidal tails, referred to as the Sgr stellar stream. In this talk, I will discuss how the population of low-metallicity ([Fe/H] < -2) stars in Sgr stream are dynamically hotter than the bulk of this substructure. By comparison with an available state-of-the-art N-body model of the Sgr system, I will show how this finding implies that this dwarf galaxy was capable of developing a metallicity gradient prior to its accretion by the Milky Way. In order to quantify this phenomenon, we used the same N-body simulation to generate a grid of Sgr models with artificial metallicity gradients applied to them. Then, by comparison with present-day observations of the stream’s stellar populations, we were able to estimate the original radial metallicity variation in Sgr dSph prior to its infall to be at the level of surviving Milky Way satellites of similar mass.