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Substructure at High Speed II: The Local Escape Velocity and Milky Way Mass with Gaia DR2

Necib, Lina and Lin, Tongyan (2021) Substructure at High Speed II: The Local Escape Velocity and Milky Way Mass with Gaia DR2. . (Unpublished)

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Measuring the escape velocity of the Milky Way is critical in obtaining the mass of the Milky Way, understanding the dark matter velocity distribution, and building the dark matter density profile. In Necib & Lin (2021), we introduced a strategy to robustly measure the escape velocity. Our approach takes into account the presence of kinematic substructures by modeling the tail of the stellar distribution with multiple components, including the stellar halo and the debris flow called the Gaia Sausage (Enceladus). In doing so, we can test the robustness of the escape velocity measurement for different definitions of the "tail" of the velocity distribution, and the consistency of the data with different underlying models. In this paper, we apply this method to the second data release of Gaia and find that a model with at least two components is preferred. Based on a fit with three bound components to account for the disk, relaxed halo, and the Gaia Sausage, we find the escape velocity of the Milky Way at the solar position to be v_(esc) = 484.6^(+17.8)_(−7.4) km/s. Assuming a Navarro-Frenck-White dark matter profile, and taken in conjunction with a recent measurement of the circular velocity at the solar position of v_c = 230±10 km/s, we find a Milky Way concentration of c_(200) = 13.8^(+6.0)_(−4.3) and a mass of M_(200) = 7.0^(+1.9)_(−1.2)×10¹¹M⊙, which is considerably lighter than previous measurements.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Necib, Lina0000-0003-2806-1414
Lin, Tongyan0000-0003-4969-3285
Additional Information:We are grateful to I. Moult for early discussions and collaboration on the project, and to M. Lisanti for helpful feedback. We would also like to thank L. Anderson, A. Bonaca, G. Collin, A. Deason, P. Hopkins, A. Ji, and J. Johnson for helpful conversations. This work was performed in part at Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1607611. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under Contract No. DEAC02- 05CH11231. LN is supported by the DOE under Award Number DESC0011632, the Sherman Fairchild fellowship, the University of California Presidential fellowship, and the fellowship of theoretical astrophysics at Carnegie Observatories. TL is supported by an Alfred P. Sloan Research Fellowship and Department of Energy (DOE) grant DE-SC0019195. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www., processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www. Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.
Group:Walter Burke Institute for Theoretical Physics
Funding AgencyGrant Number
Department of Energy (DOE)DE-AC02-05CH11231
Department of Energy (DOE)DE-SC0011632
Sherman Fairchild FoundationUNSPECIFIED
University of CaliforniaUNSPECIFIED
Carnegie ObservatoriesUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Department of Energy (DOE)DE-SC0019195
Gaia Multilateral AgreementUNSPECIFIED
Record Number:CaltechAUTHORS:20210329-142150370
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108574
Deposited By: Tony Diaz
Deposited On:30 Mar 2021 18:22
Last Modified:09 Apr 2021 20:48

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