VELOCITY DISPERSION PROFILE OF THE MILKY WAY HALO

Journal Article · Fri Jan 15 04:00:00 EST 2010 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.1088/0004-6256/139/1/59; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21301464

Brown, Warren R; Geller, Margaret J; Kenyon, Scott J ^[1]; Diaferio, Antonaldo ^[2]

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1. Smithsonian Astrophysical Observatory, 60 Garden St., Cambridge, MA 02138 (United States)
2. Dipartimento di Fisica Generale 'Amedeo Avogadro', Universita degli Studi di Torino, Via P. Giuria 1, I-10125 Torino (Italy)

We present a spectroscopic sample of 910 distant halo stars from the Hypervelocity Star survey from which we derive the velocity dispersion profile of the Milky Way halo. The sample is a mix of 74% evolved horizontal branch stars and 26% blue stragglers. We estimate distances to the stars using observed colors, metallicities, and stellar evolution tracks. Our sample contains twice as many objects with R > 50 kpc as previous surveys. We compute the velocity dispersion profile in two ways: with a parametric method based on a Milky Way potential model and with a non-parametric method based on the caustic technique originally developed to measure galaxy cluster mass profiles. The resulting velocity dispersion profiles are remarkably consistent with those found by two independent surveys based on other stellar populations: the Milky Way halo exhibits a mean decline in radial velocity dispersion of -0.38 {+-} 0.12 km s{sup -1} kpc{sup -1} over 15 < R < 75 kpc. This measurement is a useful basis for calculating the total mass and mass distribution of the Milky Way halo.

• OSTI ID: 21301464
• Journal Information: Astronomical Journal (New York, N.Y. Online), Journal Name: Astronomical Journal (New York, N.Y. Online) Journal Issue: 1 Vol. 139; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
99 GENERAL AND MISCELLANEOUS
GALAXY CLUSTERS
MASS
MASS DISTRIBUTION
MILKY WAY
RADIAL VELOCITY
STAR EVOLUTION
STARS