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The Mass of the Galaxy from Large Samples of Field Horizontal-Branch Stars in the SDSS Early Data Release

Published online by Cambridge University Press:  26 May 2016

Timothy C. Beers ,
Masashi Chiba ,
Tsuyoshi Sakamoto ,
Ron Wilhelm ,
Carlos Allende Prieto ,
Jesper Sommer-Larsen ,
Heidi J. Newberg ,
Brian Yanny ,
Brian Marsteller  and
Jeffrey R. Pier
Timothy C. Beers
Affiliation:
Dept. of Physics & Astronomy, Michigan State University, E. Lansing, MI, USA
Masashi Chiba
Affiliation:
Astronomical Institute, Tohoku University, Sendai, Japan
Tsuyoshi Sakamoto
Affiliation:
Dept. of Astronomical Science, the Graduate University for Advanced Studies, Mitaka, Japan
Ron Wilhelm
Affiliation:
Dept. of Physics, Texas Tech University, Lubbock, TX, USA
Carlos Allende Prieto
Affiliation:
McDonald Observatory and Dept. of Astronomy, University of Texas, Austin, TX, USA
Jesper Sommer-Larsen
Affiliation:
Theoretical Astrophysics Center, Copenhagen, Denmark
Heidi J. Newberg
Affiliation:
Dept. of Physics & Astronomy, Rensselaer Polytechnical University, Troy, NY, USA
Brian Yanny
Affiliation:
Fermi National Accelerator Lab, Batavia, IL, USA
Brian Marsteller
Affiliation:
Dept. of Physics & Astronomy, Michigan State University, E. Lansing, MI, USA
Jeffrey R. Pier
Affiliation:
US Naval Observatory, Flagstaff Station, Flagstaff, AZ, USA

Abstract

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We present a new estimate of the mass of the Milky Way, making use of a large sample of 955 field horizontal-branch (FHB) stars from the Early Data Release of the Sloan Digital Sky Survey. This sample of stars has been classified on the basis of an automated analysis approach, in combination with other methods, in order to obtain estimates of the physical parameters of the stars, i.e., Teff, log g, [Fe/H], and should be relatively free of contamination from halo blue stragglers. the stars all have measured radial velocities and photometric distance estimates, and the sample includes objects as distant as ~ 75 kpc from the Galactic center. Application of a Bayesian likelihood method, for a specific model of the Galaxy, indicates that the total mass of the Galaxy lies in the range 1.5 − 4.0 × 1012 M⊙. Our sample appears to reveal a clear signature of a dual halo population of FHB stars, with the boundary between the inner and outer halo around 20 kpc, and the possibility of rather striking differences in the rotational properties of the Galaxy at low metallicity.

Type
Part 6: The Galaxy
Information
Symposium - International Astronomical Union , Volume 220: Dark Matter in Galaxies , 2004 , pp. 195 - 200
Copyright
Copyright © Astronomical Society of the Pacific 2004 

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