Astronomy and Astrophysics – Astrophysics – Galaxy Astrophysics
Scientific paper
2011-04-16
Astronomy and Astrophysics
Astrophysics
Galaxy Astrophysics
13 pages, 12 figures. Accepted for publication by MNRAS
Scientific paper
We introduce a new maximum likelihood method to model the density profile of Blue Horizontal Branch and Blue Straggler stars and apply it to the Sloan Digital Sky Survey Data Release 8 (DR8) photometric catalogue. There are a large number (20,000) of these tracers available over an impressive 14,000 square degrees in both Northern and Southern Galactic hemispheres, and they provide a robust measurement of the shape of the Milky Way stellar halo. After masking out stars in the vicinity of the Virgo Overdensity and the Sagittarius stream, the data are consistent with a smooth, oblate stellar halo with a density that follows a broken power-law. The best fitting model has an inner slope = 2.3 and an outer slope = 4.6, together with a break radius occurring at 27 kpc and a constant halo flattening (that is, ratio of minor axis to major axis) of q = 0.6. Although a broken power-law describes the density fall-off most adequately, it is also well fit by an Einasto profile. There is no strong evidence for variations in flattening with radius, or for triaxiality of the stellar halo.
Belokurov Vasily
Deason Alis J.
Evans Wyn N.
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