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Substructure at High Speed I: Inferring the Escape Velocity in the Presence of Kinematic Substructure

Necib, Lina and Lin, Tongyan (2021) Substructure at High Speed I: Inferring the Escape Velocity in the Presence of Kinematic Substructure. . (Unpublished)

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The local escape velocity provides valuable inputs to the mass profile of the Galaxy, and requires understanding the tail of the stellar speed distribution. Following Leonard & Tremaine (1990), various works have since modeled the tail of the stellar speed distribution as ∝(v_(esc)−v)^k, where v_(esc) is the escape velocity, and k is the slope of the distribution. In such studies, however, these two parameters were found to be largely degenerate and often a narrow prior is imposed on k in order to constrain v_(esc). Furthermore, the validity of the power law form is likely to break down in the presence of multiple kinematic substructures. In this paper, we introduce a strategy that for the first time takes into account the presence of kinematic substructure. We model the tail of the velocity distribution as a sum of multiple power laws without imposing strong priors. Using mock data, we show the robustness of this method in the presence of kinematic structure that is similar to the recently-discovered Gaia Sausage. In a companion paper, we present the new measurement of the escape velocity and subsequently the mass of the Milky Way using Gaia DR2 data.

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. DE-AC02-05CH11231. 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.
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
Record Number:CaltechAUTHORS:20210331-082522650
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108589
Deposited By: Tony Diaz
Deposited On:31 Mar 2021 15:50
Last Modified:09 Apr 2021 20:49

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