The effects of dynamical substructure on Milky Way mass estimates from the high-velocity tail of the local stellar halo

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Grand, RJJ orcid iconORCID: 0000-0001-9667-1340, Deason, AJ orcid iconORCID: 0000-0001-6146-2645, White, SDM orcid iconORCID: 0000-0002-1061-6154, Simpson, CM orcid iconORCID: 0000-0001-9985-1814, Gómez, FA, Marinacci, F orcid iconORCID: 0000-0003-3816-7028 and Pakmor, R orcid iconORCID: 0000-0003-3308-2420 (2019) The effects of dynamical substructure on Milky Way mass estimates from the high-velocity tail of the local stellar halo. Monthly Notices of the Royal Astronomical Society: Letters, 487 (1). L720-LL76. ISSN 1745-3925

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Abstract

We investigate the impact of dynamical streams and substructure on estimates of the local escape speed and total mass of Milky-Way-mass galaxies from modelling the high-velocity tail of local halo stars. We use a suite of high-resolution magnetohydrodynamical cosmological zoom-in simulations that resolve phase space substructure in local volumes around solar-like positions. We show that phase space structure varies significantly between positions in individual galaxies and across the suite. Substructure populates the high-velocity tail unevenly and leads to discrepancies in the mass estimates. We show that a combination of streams, sample noise, and truncation of the high-velocity tail below the escape speed leads to a distribution of mass estimates with a median that falls below the true value by ${\sim } 20 {{\ \rm per\ cent}}$, and a spread of a factor of 2 across the suite. Correcting for these biases, we derive a revised value for the Milky Way mass presented in Deason et al. of $1.29 ^{+0.37}_{-0.47} \times 10^{12}\, \rm M_{\odot }$.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2019 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical and Space Sciences
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press (OUP)
Date of acceptance: 3 June 2019
Date of first compliant Open Access: 19 April 2023
Date Deposited: 19 Apr 2023 11:52
Last Modified: 05 Jul 2025 08:45
DOI or ID number: 10.1093/mnrasl/slz092
URI: https://researchonline.ljmu.ac.uk/id/eprint/19321
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