Astronomy and Astrophysics – Astrophysics – Galaxy Astrophysics
Scientific paper
2010-10-12
The Astrophysical Journal Letters, 727, L14 (2011)
Astronomy and Astrophysics
Astrophysics
Galaxy Astrophysics
Accepted for publication in ApJ Letters. Minor revisions from version 1
Scientific paper
10.1088/2041-8205/727/1/L14
We develop a technique to investigate the possibility that some of the recently discovered ultra-faint dwarf satellites of the Milky Way might be cusp caustics rather than gravitationally self-bound systems. Such cusps can form when a stream of stars folds, creating a region where the projected 2-D surface density is enhanced. In this work, we construct a Poisson maximum likelihood test to compare the cusp and exponential models of any substructure on an equal footing. We apply the test to the Hercules dwarf (d ~ 113 kpc, M_V ~ -6.2, e ~ 0.67). The flattened exponential model is strongly favored over the cusp model in the case of Hercules, ruling out at high confidence that Hercules is a cusp catastrophe. This test can be applied to any of the Milky Way dwarfs, and more generally to the entire stellar halo population, to search for the cusp catastrophes that might be expected in an accreted stellar halo.
Hogg David Wardell
Willman Beth
Zolotov Adi
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