Milky Way mass constraints from the Galactic satellite gap

Marius Cautun; Carlos S. Frenk; Rien van de Weygaert; Wojciech A. Hellwing; Bernard J. T. Jones

doi:10.1093/mnras/stu1849

paper

Milky Way mass constraints from the Galactic satellite gap

arXiv:1405.7697 · doi:10.1093/mnras/stu1849

Abstract

We use the distribution of maximum circular velocities, $V_{ma x}$ , of satellites in the Milky Way (MW) to constrain the virial mass, $M_{200}$ , of the Galactic halo under an assumed prior of a $Λ$ CDM universe. This is done by analysing the subhalo populations of a large sample of halos found in the Millennium II cosmological simulation. The observation that the MW has at most three subhalos with $V_{ma x} \geq 30 k m / s$ requires a halo mass $M_{200} \leq 1.4 \times 1 0^{12} M_{⊙}$ , while the existence of the Magellanic Clouds (assumed to have $V_{ma x} \geq 60 k m / s$ ) requires $M_{200} \geq 1.0 \times 1 0^{12} M_{⊙}$ . The first of these conditions is necessary to avoid the "too-big-to-fail" problem highlighted by Boylan-Kolchin et al., while the second stems from the observation that massive satellites like the Magellanic Clouds are rare. When combining both requirements, we find that the MW halo mass must lie in the range $0.25 \leq M_{200} / (1 0^{12} M_{⊙}) \leq 1.4$ at $90%$ confidence. The gap in the abundance of Galactic satellites between $30 k m / s \leq V_{ma x} \leq 60 k m / s$ places our galaxy in the tail of the expected satellite distribution.

arXiv comment13 pages, 9 figures, updated to match published version in MNRAS

Milky Way mass constraints from the Galactic satellite gap

Abstract

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