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The Light Side and The Dark Side of the Milky Way Halo

Published online by Cambridge University Press:  06 January 2014

Prajwal R. Kafle ,
Sanjib Sharma ,
Geraint F. Lewis  and
Joss Bland-Hawthorn
Prajwal R. Kafle
Affiliation:
Sydney Institute for Astronomy, School of Physics, The University of Sydney email: p.kafle@physics.usyd.edu.au
Sanjib Sharma
Affiliation:
Sydney Institute for Astronomy, School of Physics, The University of Sydney email: p.kafle@physics.usyd.edu.au
Geraint F. Lewis
Affiliation:
Sydney Institute for Astronomy, School of Physics, The University of Sydney email: p.kafle@physics.usyd.edu.au
Joss Bland-Hawthorn
Affiliation:
Sydney Institute for Astronomy, School of Physics, The University of Sydney email: p.kafle@physics.usyd.edu.au
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Abstract

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We present our recent measurement of the kinematics of the Milky Way stellar halo (Light Side) and the derived mass of the dark matter halo (Dark Side) using the Jeans analysis. A tangential dip in the velocity anisotropy profile at r ~ 17 kpc (Kafle et al. 2012), and a distinct difference of ~65 kms−1 in the mean azimuthal velocity and the r.m.s dispersion of the most metal-rich and the metal-poor Blue Horizontal Branch stars we find (Kafle et al. 2013) are reported. The implications of this on the current controversial issue of an existence of the two-components in the halo are also discussed.

Aided with the kinematic measurements of the light side, we demonstrate how we infer the dynamical property of the dark side. Considering a realistic three component galaxy model (Hernquist bulge, Miyamoto-Nagai disk and NFW halo), we estimate the virial mass of the Galaxy to be Mvir = 1.2+0.5−0.4 × 1012M⊙ (Kafle et al. 2012). We also show that the rotation curve of the Galaxy has undulations similar to what have also been seen in the studies of the HI gas (Sofue et al. 2009).

Keywords

Galaxy:haloGalaxy:kinematics and dynamicsstars:horizontal-branch
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 9 , Symposium S298: Setting the scene for Gaia and LAMOST , May 2013 , pp. 416
Copyright
Copyright © International Astronomical Union 2014 

References

Sofue, Y., Honma, M., Omodoka, T. 2009, PASJ, 61, 227CrossRefGoogle Scholar
Kafle, P. R., Sharma, S., Lewis, G. F., & Bland-Hawthorn, J. 2012, ApJ, 761, 98CrossRefGoogle Scholar
Kafle, P. R., Sharma, S., Lewis, G. F., & Bland-Hawthorn, J. 2013, MNRAS 430 2973–2978CrossRefGoogle Scholar