Identifying Star Streams in the Milky Way Halo

Abstract

We develop statistical methods for identifying star streams in the halo of the Milky Way galaxy that exploit observed spatial and radial velocity distributions. Within a great circle, departures of the observed spatial distribution from random provide a measure of the likelihood of a potential star stream. Comparisons between the radial velocity distribution within a great circle and the radial velocity distribution of the entire sample also measure the statistical significance of potential streams. The radial velocities enable construction of a more powerful joint statistical test for identifying star streams in the Milky Way halo. Applying our method to halo stars in the Hypervelocity Star (HVS) survey, we detect the Sagittarius stream at high significance. Great circle counts and comparisons with theoretical models suggest that the Sagittarius stream comprises 10% to 17% of the halo stars in the HVS sample. The population of blue stragglers and blue horizontal branch stars varies along the stream and is a potential probe of the distribution of stellar populations in the Sagittarius dwarf galaxy prior to disruption.

10 pages, 10 figures, submitted to ApJ

References in corpus (18)

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Cited by in corpus (6)

• MMT Hypervelocity Star Survey III: A Complete Survey of Faint B-type Stars in the Northern Milky Way Halo
• Hypervelocity Star Candidates in the SEGUE G & K Dwarf Sample
• Stellar Velocity Dispersion and Anisotropy of the Milky Way Inner Halo
• Distributing points uniformly on the unit sphere under a mirror reflection symmetry constraint
• Report on Optimal Substructure Techniques for Stellar, Gas and Combined Samples
• Pseudometrically Constrained Centroidal Voronoi Tessellations: Generating uniform antipodally symmetric points on the unit sphere with a novel acceleration strategy and its applications to Diffusion and 3D radial MRI