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Durham University

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Publication details for Dr Alis Deason

Grand, Robert J J, Deason, Alis J, White, Simon D M, Simpson, Christine M, Gómez, Facundo A, Marinacci, Federico & Pakmor, Rüdiger (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.

Author(s) from Durham

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⊙
⁠.