We use cookies to ensure that we give you the best experience on our website. You can change your cookie settings at any time. Otherwise, we'll assume you're OK to continue.

Durham University

Research & business

View Profile

Publication details for Dr Alis Deason

Deason, A.J., Belokurov, V. & Weisz, D.R. (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.

Author(s) from Durham


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.