THE EATING HABITS OF MILKY WAY-MASS HALOS: DESTROYED DWARF SATELLITES AND THE METALLICITY DISTRIBUTION OF ACCRETED STARS

• Published in: The Astrophysical journal 2016-04, Vol.821 (1), p.5-5
• Main Authors: Deason, Alis J., Mao, Yao-Yuan, Wechsler, Risa H.
• Format: Article
• Language: English
• Subjects: ASTRONOMY AND ASTROPHYSICS; Computer simulation; dwarf; Fossils; Galactic halos; galaxies: dwarf; galaxies: interactions; Galaxy: formation; Galaxy: halo; Galaxy: stellar content; halo; Halos; interactions; Local Group; Metallicity; Progenitors (astrophysics); Stars; stellar content; Stellar mass
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.3847/0004-637X/821/1/5

ABSTRACT We study the mass spectrum of destroyed dwarfs that contribute to the accreted stellar mass of Milky Way (MW)-mass (Mvir ∼ 1012.1 M ) halos using a suite of 45 zoom-in dissipationless simulations. Empirical models are employed to relate (peak) subhalo mass to dwarf stellar mass, and we use constraints from z = 0 observations and hydrodynamical simulations to estimate the metallicity distribution of the accreted stellar material. The dominant contributors to the accreted stellar mass are relatively massive dwarfs with Mstar ∼ 108-1010M . Halos with more quiescent accretion histories tend to have lower mass progenitors (108-109 M ), and lower overall accreted stellar masses. Ultra-faint mass (Mstar < 105 M ) dwarfs contribute a negligible amount ( 108 M can contribute a considerable fraction (∼20%-60%) of metal-poor stars if their metallicity distributions have significant metal-poor tails. Finally, we find that the generic assumption of a quiescent assembly history for the MW halo seems to be in tension with the mass spectrum of its surviving dwarfs. We suggest that the MW could be a "transient fossil"; a quiescent halo with a recent accretion event(s) that disguises the preceding formation history of the halo.