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

Grand, Robert JJ; Deason, Alis J; White, Simon DM; Simpson, Christine M; Gómez, Facundo A; Marinacci, Federico; Pakmor, Rüdiger

doi:10.1093/mnrasl/slz092

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

Grand, Robert JJ; Deason, Alis J; White, Simon DM; Simpson, Christine M; Gómez, Facundo A; Marinacci, Federico; Pakmor, Rüdiger

Authors

Robert JJ Grand

Dr Alis Deason alis.j.deason@durham.ac.uk
Associate Professor

Simon DM White

Christine M Simpson

Facundo A Gómez

Federico Marinacci

Rüdiger Pakmor

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 ∼20 per cent ∼20 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 × 10 12 M ⊙ 1.29−0.47+0.37×1012M⊙ ⁠.

Citation

Grand, R. J., Deason, A. J., White, S. D., Simpson, C. M., Gómez, F. A., Marinacci, F., & Pakmor, R. (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), L72-L76. https://doi.org/10.1093/mnrasl/slz092

Journal Article Type	Article
Acceptance Date	Jun 3, 2019
Online Publication Date	Jun 18, 2019
Publication Date	Jul 31, 2019
Deposit Date	Sep 13, 2019
Publicly Available Date	Sep 13, 2019
Journal	Monthly Notices of the Royal Astronomical Society: Letters
Electronic ISSN	1745-3933
Publisher	Oxford University Press
Peer Reviewed	Peer Reviewed
Volume	487
Issue	1
Pages	L72-L76
DOI	https://doi.org/10.1093/mnrasl/slz092

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This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society: Letters ©: 2019 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.