The progenitors of the Milky Way stellar halo: big bricks favoured over little bricks

Deason, A.J.; Belokurov, V.; Weisz, D.R.

Abstract

We present a census of blue horizontal branch (BHB) and blue straggler (BS) stars belonging to dwarf galaxies and globular clusters, and compare these counts to that of the Milky Way stellar halo. We find, in agreement with earlier studies, that the ratio of BS-to-BHB stars in these satellite populations is dependent on stellar mass. Dwarf galaxies show an increasing BS-to-BHB ratio with luminosity. In contrast, globular clusters display the reverse trend, with NBS/NBHB (≲ 1) decreasing with luminosity. The faintest (L < 105 Lȯ) dwarfs have similar numbers of BS and BHB stars (NBS/NBHB ∼ 1), whereas more-massive dwarfs tend to be dominated by BS stars (NBS/NBHB ∼ 2–40). We find that the BS-to-BHB ratio in the stellar halo is relatively high (NBS/NBHB ∼ 5–6), and thus inconsistent with the low ratios found in both ultra-faint dwarfs and globular clusters. Our results favour more-massive dwarfs as the dominant ‘building blocks’ of the stellar halo, in good agreement with current predictions from Λ cold dark matter models.

Citation

Deason, A., Belokurov, V., & Weisz, D. (2015). The progenitors of the Milky Way stellar halo: big bricks favoured over little bricks. Monthly Notices of the Royal Astronomical Society: Letters, 448(1), L77-L81. https://doi.org/10.1093/mnrasl/slv001

• Journal Article Type: Article
• Acceptance Date: Jan 3, 2015
• Online Publication Date: Feb 2, 2015
• Publication Date: Mar 21, 2015
• Deposit Date: Feb 20, 2017
• Publicly Available Date: Mar 27, 2017
• Journal: Monthly Notices of the Royal Astronomical Society: Letters
• Electronic ISSN: 1745-3933
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 448
• Issue: 1
• Pages: L77-L81
• DOI: https://doi.org/10.1093/mnrasl/slv001
• Public URL: https://durham-repository.worktribe.com/output/1364097
• Related Public URLs: https://arxiv.org/abs/1501.02806