A tale of two populations: surviving and destroyed dwarf galaxies and the build up of the Milky Way's stellar halo

Understand

We use magneto-hydrodynamical simulations of Milky Way-mass haloes from the Auriga project to examine the properties of surviving and destroyed dwarf galaxies that are accreted by these haloes over cosmic time.

• We show that the combined luminosity function of surviving and destroyed dwarfs at infall is similar in the various Auriga haloes, and is dominated by the destroyed dwarfs.
• There is, however, a strong dependence on infall time: destroyed dwarfs have typically early infall times, $t_{infall}<6$ Gyr, whereas the majority of dwarfs accreted at $t_{infall}>10$ Gyr have survived to the present day.
• Because of their late infall the surviving satellites today had higher metallicites at infall than their destroyed counterparts of similar infall mass; the difference is even more pronounced for the present-day metallicites of satellites, many of which continue to form stars after infall.