Is the Sgr dSph a dark matter dominated system?

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 106 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 1.2kpc or higher; furthermore, this galaxy could have been immersed in a dark halo with a mass higher than 108M⊙. These results are important for the construction of a model of the formation of Sgr dSph.