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The Milky Way total mass profile as inferred from Gaia DR2

Cautun, Marius; Benítez-Llambay, Alejandro; Deason, Alis J.; Frenk, Carlos S.; Fattahi, Azadeh; Gómez, Facundo A.; Grand, Robert J.J.; Oman, Kyle A.; Navarro, Julio F.; Simpson, Christine M.

The Milky Way total mass profile as inferred from Gaia DR2 Thumbnail


Marius Cautun

Alejandro Benítez-Llambay

Facundo A. Gómez

Robert J.J. Grand

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Dr Kyle Oman
Assistant Professor - Royal Society Dorothy Hodgkin Fellow

Julio F. Navarro

Christine M. Simpson


We determine the Milky Way (MW) mass profile inferred from fitting physically motivated models to the Gaia DR2 Galactic rotation curve and other data. Using various hydrodynamical simulations of MW-mass haloes, we show that the presence of baryons induces a contraction of the dark matter (DM) distribution in the inner regions, r . 20 kpc. We provide an analytic expression that relates the baryonic distribution to the change in the DM halo profile. For our galaxy, the contraction increases the enclosed DM halo mass by factors of roughly 1.3, 2 and 4 at radial distances of 20, 8 and 1 kpc, respectively compared to an uncontracted halo. Ignoring this contraction results in systematic biases in the inferred halo mass and concentration. We provide a best-fitting contracted NFW halo model to the MW rotation curve that matches the data very well†. The best-fit has a DM halo mass, MDM 200 = 0.97+0.24 −0.19×1012 M, and concentration before baryon contraction of 9.4 +1.9 −2.6 , which lie close to the median halo mass–concentration relation predicted in ΛCDM. The inferred total mass, Mtotal 200 = 1.08+0.20 −0.14 × 1012 M, is in good agreement with recent measurements. The model gives a MW stellar mass of 5.04+0.43 −0.52 × 1010 M and infers that the DM density at the Solar position is ρ DM = 8.8 +0.5 −0.5 ×10−3 M pc−3 ≡ 0.33+0.02 −0.02 GeV cm−3 . The rotation curve data can also be fitted with an uncontracted NFW halo model, but with very different DM and stellar parameters. The observations prefer the physically motivated contracted NFW halo, but the measurement uncertainties are too large to rule out the uncontracted NFW halo.


Cautun, M., Benítez-Llambay, A., Deason, A. J., Frenk, C. S., Fattahi, A., Gómez, F. A., …Simpson, C. M. (2020). The Milky Way total mass profile as inferred from Gaia DR2. Monthly Notices of the Royal Astronomical Society, 494(3), 4291-4313.

Journal Article Type Article
Acceptance Date Apr 8, 2020
Online Publication Date Apr 17, 2020
Publication Date May 31, 2020
Deposit Date Apr 19, 2020
Publicly Available Date Apr 20, 2020
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 494
Issue 3
Pages 4291-4313


Accepted Journal Article (1.5 Mb)

Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2020 The Author(s) . Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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