KINEMATICS OF THE STELLAR HALO AND THE MASS DISTRIBUTION OF THE MILKY WAY USING BLUE HORIZONTAL BRANCH STARS

Here, we present a kinematic study of the Galactic halo out to a radius of ~60 kpc, using 4664 blue horizontal branch stars selected from the SDSS/SEGUE survey to determine key dynamical properties. Using a maximum likelihood analysis, we determine the velocity dispersion profiles in spherical coord...

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Bibliographic Details
Published in:The Astrophysical journal 2012-12, Vol.761 (2), p.1-17
Main Authors: KAFLE, Prajwal R, SHARMA, Sanjib, LEWIS, Geraint F, BLAND-HAWTHORN, Joss
Format: Article
Language:English
Subjects:
ANISOTROPY
ASTRONOMY
ASTROPHYSICS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BINARY STARS
Computer simulation
COMPUTERIZED SIMULATION
Constants
Dispersions
Earth, ocean, space
Exact sciences and technology
Halos
Horizontal branch stars
Kinematics
MASS
MASS DISTRIBUTION
Mathematical analysis
MAXIMUM-LIKELIHOOD FIT
MILKY WAY
NONLUMINOUS MATTER
PROPER MOTION
RADIAL VELOCITY
SPHERICAL CONFIGURATION
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Summary:Here, we present a kinematic study of the Galactic halo out to a radius of ~60 kpc, using 4664 blue horizontal branch stars selected from the SDSS/SEGUE survey to determine key dynamical properties. Using a maximum likelihood analysis, we determine the velocity dispersion profiles in spherical coordinates ([sigma] sub(r), [sigma] sub([theta]), [sigma] sub([phi])) and the anisotropy profile ([beta]). The radial velocity dispersion profile ([sigma] sub(r)) is measured out to a galactocentric radius of r ~ 60 kpc, but due to the lack of proper-motion information, [sigma] sub([theta]), [sigma] sub([phi]), and [beta] could only be derived directly out to r ~ 25 kpc. In the outer parts, in the range 25 < r/kpc < 56, we predict the profile to be roughly constant with a value of [beta] approximately 0.5. The newly discovered kinematic anomalies are shown not to arise from halo substructures. We also studied the anisotropy profile of simulated stellar halos formed purely by accretion and found that they cannot reproduce the sharp dip seen in the data. From the Jeans equation, we compute the stellar rotation curve ([upsilon] sub(circ)) of the Galaxy out to r ~ 25 kpc.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637x/761/2/98