Dwarf Galaxies in the Galactic Potential as probes of its internal structure

Abstract: Satellite galaxies on bound orbits around the Milky Way (MW) are constantly subject to tidal forces from the MW. If the tidal forces are large enough, they may strip the outermost stars of the satellite, that in turn distribute themselves in long elongated stellar streams. These stellar streams are good probes of the Galactic potential due to the constraints they place on the structure of the potential they reside in. Through numerical integration of satellite galaxy disruptions, we perform a qualitative study on how a dynamically significant dark matter (DM) disk affects the evolution of associated stellar streams. Apart from the ordinary MW potential with an assumed total DM density of ρtot ∼ 0.008M⊙pc−3 at the solar position, we consider two DM disks, one with ρDDISK(R⊙) ∼ 0.01M⊙pc−3 and the other with ρDDISK(R⊙) ∼ 0.065M⊙pc−3. We find that for high velocity encounters where the satellite passes through the disk at a pericenter ∼ 4kpc, traces of tidal shocks can be seen as gaps in the stellar streams’ offsets in an energy-angular momentum plane. Based on the ranges in offsets, we conclude that the largest of these densities is highly unlikely to be realistic for the MW.