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Galactic mass and anisotropy profile with halo K-giant and blue horizontal branch stars from LAMOST/SDSS and Gaia

Published online by Cambridge University Press:  14 May 2020

Sarah A. Bird Open the ORCID record for Sarah A. Bird [Opens in a new window] ,
Xiang-Xiang Xue ,
Chao Liu ,
Juntai Shen ,
Chris Flynn  and
Chengqun Yang
Sarah A. Bird
Affiliation:
Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Beijing100012, China emails: sarahbird@nao.cas.cn, xuexx@nao.cas.cn, liuchao@nao.cas.cn
Xiang-Xiang Xue
Affiliation:
Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Beijing100012, China emails: sarahbird@nao.cas.cn, xuexx@nao.cas.cn, liuchao@nao.cas.cn
Chao Liu
Affiliation:
Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Beijing100012, China emails: sarahbird@nao.cas.cn, xuexx@nao.cas.cn, liuchao@nao.cas.cn
Juntai Shen
Affiliation:
Department of Astronomy, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai200240, China email: jtshen@sjtu.edu.cn Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai200030, China College of Astronomy and Space Sciences, University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing100049, China
Chris Flynn
Affiliation:
Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Post Office Box 218, Hawthorn, VIC 3122, Australia email: cflynn@swin.edu.au
Chengqun Yang
Affiliation:
Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Beijing100012, China emails: sarahbird@nao.cas.cn, xuexx@nao.cas.cn, liuchao@nao.cas.cn College of Astronomy and Space Sciences, University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing100049, China
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Abstract

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A major uncertainty in the determination of the mass profile of the Milky Way using stellar kinematics in the halo is the poorly determined anisotropy parameter, , where σr is the Galactocentric radial velocity dispersion, and σθ and σφ are the tangential components of the velocity dispersion. We have used a sample of over 24,000 Galactic halo K giant and blue horizontal branch stars from the LAMOST stellar spectroscopic survey and SDSS/SEGUE, combined with proper motions from Gaia Data Release 2, to measure β(rgc) over a wide range of Galactocentric distances rgc from 5 to 80 kpc. Kinematic substructures have been carefully removed to reveal the underlying diffuse stellar halo prior to measuring β. We find that orbits are generally radial (β > 0) and β is constant out to distances of about 40 kpc, with a dependence on metallicity of the stars, such that β declines with lower metallicity. Similar behavior is seen in both the K giant and BHB samples.

Keywords

galaxies: individual (Milky Way)Galaxy: haloGalaxy: kinematics and dynamicsGalaxy: stellar contentstars: individual (BHB)stars: individual (K giants)stars: kinematics and dynamics
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 14 , Symposium S353: Galactic Dynamics in the Era of Large Surveys , June 2019 , pp. 91 - 95
Copyright
© International Astronomical Union 2020

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