• DOI:10.1093/mnrasl/slz092
• Corpus ID: 165163524

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

@article{Grand2019TheEO,
  title={The effects of dynamical substructure on Milky Way mass estimates from the high-velocity tail of the local stellar halo},
  author={Robert J. J. Grand and Alis J. Deason and Simon D. M. White and Christine M. Simpson and Facundo A. G'omez and Federico Marinacci and R{\"u}diger Pakmor},
  journal={Monthly Notices of the Royal Astronomical Society: Letters},
  year={2019}
}

• R. Grand, A. Deason, +4 authors R. Pakmor
• Published 23 May 2019
• Physics
• Monthly Notices of the Royal Astronomical Society: Letters

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⊙
⁠.