2020/02/29 by Azadeh Fattahi, Alis J. Deason, Carlos S. Frenk +6 · 1 citation
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.1093/mnras/staa2221
Replaced with the accepted version after minor modifications
arxiv created 2020/10/07 · arxiv updated 2020/10/08
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, tinfall<6 Gyr, whereas the majority of dwarfs accreted at tinfall>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. In agreement with previous work, we find that a small number of relatively massive destroyed dwarf galaxies dominate the mass of the stellar haloes. However, there is a significant radial dependence: while 90 per cent of the mass in the inner regions (< 20 kpc) is contributed, on average, by only 3 massive progenitors, the outer regions (> 100 kpc) typically have ∼8 main progenitors of relatively lower mass. Finally, we show that a few massive progenitors dominate the metallicity distribution of accreted stars, even at the metal poor end. Contrary to common assumptions in the literature, dwarf galaxies of mass M*<107 M\odot make up less than 10 per cent of the accreted, metal poor stars ([Fe/H] < -3) in the inner 50 kpc.