Is the Sgr dSph a dark matter dominated system?

TL;DR

This study uses N-body simulations to investigate whether the Sagittarius dwarf spheroidal galaxy (Sgr dSph) was initially dominated by dark matter, finding that dark matter presence is necessary to reproduce its observed properties.

Contribution

It demonstrates through simulations that Sgr dSph likely started with a significant dark matter halo, providing new insights into its initial structure and formation.

Findings

Dark matter is essential to replicate Sgr dSph's properties.

Initial Plummer radius may have been ≥ 1.2 kpc.

Dark halo mass likely exceeded 10^8 solar masses.

Abstract

We study the evolution of possible progenitors of Sgr dSph}using several numerical N-body simulations of different dwarf spheroidal galaxies both with and without dark matter, as they orbit the Milky Way. The barionic and dark components of the dwarfs were made obeying a Plummer and NFW potentials of one million particles respectively. The Milky Way was modeled like a tree-component rigid potential and the simulations were performed using a modified Gadget-2 code. We found that none of the simulated galaxies without dark matter reproduced the physical properties observed in Sgr dSph, suggesting that, at the beginning of its evolution, Sgr dSph might have been immersed in a dark matter halo. The simulations of progenitors immersed in dark matter halos suggest that Sgr dSph at its beginning might have been an extended system, i.e. its Plummer radius could have had a value approximated to 1.2 kpc or higher; furthermore, this galaxy could have been immersed in a dark halo with a mass higher than 10^8 solar masses. These results are important for the construction of a model of the formation of Sgr dSph.