The accreted stellar halo as a window on halo assembly in L* galaxies
Abstract
Theory and observations agree that the accreted stellar haloes (ASHs) of Milky Way-like galaxies display significant scatter. I take advantage of this stochasticity to invert the link between halo assembly history (HAH) and ASH, using mock ASHs corresponding to 750 ΛCDM HAHs, sharing a final virial mass of Mh(z = 0) = 1012.25M⊙. Hosts with poor/rich ASHs assemble following orthogonal growth-patterns. Hosts with rich ASHs experience accretion events (AEs) with high virial mass ratios (HVMRs, Ms/Mh ≳ 0.1) at 0.5 ≲ zinfall ≲ 1.5, in a phase of fast growth. This maximizes the accreted stellar mass under the condition these satellites are disrupted by z = 0. At similar times, hosts with poor ASHs grow slowly through minor mergers, with only very recent HVMR AEs: this results in a globally more abundant satellite population and in distinctive surviving massive satellites (stellar mass log Ms, */M⊙ ≳ 9). Several properties of the Milky Way are in agreement with the predictions of this framework for hosts with poor, concentrated ASHs, including: (I) the recent infall of Sagittarius and Magellanic Clouds, (II) the likely higher-than-average concentration of its dark halo and (III) the signatures of fast chemical enrichment of a sizable fraction of its halo stellar populations.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- July 2017
- DOI:
- 10.1093/mnrasl/slx044
- arXiv:
- arXiv:1701.02741
- Bibcode:
- 2017MNRAS.469L..48A
- Keywords:
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- galaxies: evolution;
- galaxies: formation;
- galaxies: haloes;
- galaxies: structure;
- dark matter;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- accepted version, minor changes