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Estimating the dark matter halo mass of our Milky Way using dynamical tracers

Wang, Wenting; Han, Jiaxin; Cooper, Andrew P.; Cole, Shaun; Frenk, Carlos; Lowing, Ben

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Wenting Wang

Jiaxin Han

Andrew P. Cooper

Ben Lowing


The mass of the dark matter halo of the Milky Way can be estimated by fitting analytical models to the phase-space distribution of dynamical tracers. We test this approach using realistic mock stellar haloes constructed from the Aquarius N-body simulations of dark matter haloes in the Λ cold dark matter cosmology. We extend the standard treatment to include a Navarro–Frenk–White potential and use a maximum likelihood method to recover the parameters describing the simulated haloes from the positions and velocities of their mock halo stars. We find that the estimate of halo mass is highly correlated with the estimate of halo concentration. The best-fitting halo masses within the virial radius, R200, are biased, ranging from a 40 per cent underestimate to a 5 per cent overestimate in the best case (when the tangential velocities of the tracers are included). There are several sources of bias. Deviations from dynamical equilibrium can potentially cause significant bias; deviations from spherical symmetry are relatively less important. Fits to stars at different galactocentric radii can give different mass estimates. By contrast, the model gives good constraints on the mass within the half-mass radius of tracers even when restricted to tracers within 60 kpc. The recovered velocity anisotropies of tracers, β, are biased systematically, but this does not affect other parameters if tangential velocity data are used as constraints.


Wang, W., Han, J., Cooper, A. P., Cole, S., Frenk, C., & Lowing, B. (2015). Estimating the dark matter halo mass of our Milky Way using dynamical tracers. Monthly Notices of the Royal Astronomical Society, 453(1), 377-400.

Journal Article Type Article
Acceptance Date Jul 17, 2015
Online Publication Date Aug 13, 2015
Publication Date Oct 11, 2015
Deposit Date Feb 9, 2016
Publicly Available Date Feb 12, 2016
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 453
Issue 1
Pages 377-400
Keywords Galaxy: halo, Galaxy: kinematics and dynamics, Dark matter.


Published Journal Article (4.8 Mb)

Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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