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We present a new estimate of the mass of the Milky Way, inferred via a Bayesian approach by making use of tracers of the circular velocity in the disk plane and stars in the stellar halo, as from the publicly available galkin compilation. We use the rotation curve method to determine the dark matter distribution and total mass under different assumptions for the dark matter profile, while the total stellar mass is constrained by surface stellar density and microlensing measurements. We also include uncertainties on the baryonic morphology via Bayesian model averaging, thus converting a potential source of systematic error into a more manageable statistical uncertainty. We evaluate the robustness of our result against various possible systematics, including rotation curve data selection, uncertainty on the Sun's velocity V0, dependence on the dark matter profile assumptions, and choice of priors. We find the Milky Way's dark matter virial mass to be log10M200 DM/ Mo˙ = 11.92+0.06 -0.05(stat)±0.28±0.27(syst) (M200 DM=8.3+1.2 -0.9(stat)×1011 Mo˙). We also apply our framework to Gaia DR2 rotation curve data and find good statistical agreement with the above results.

Astrocent Nicolaus Copernicus Astronomical Center Polish Academy of Sciences, ul. Bartycka 18

ICTP-SAIFR IFT-UNESP, R. Dr. Bento Teobaldo Ferraz 271

National Institute of Chemical Physics and Biophysics, Rävala 10

Physics Department Astrophysics Group Imp. Centre for Inference and Cosmology Blackett Laboratory Imperial College London, Prince Consort Rd

Università di Napoli Federico II INFN Sezione di Napoli Complesso Universitario di Monte S. Angelo, via Cintia

Data Science Institute William Penney Laboratory Imperial College London

SISSA Data Science Excellence Department, Via Bonomea 265

ICTP-SAIFR IFT-UNESP, R. Dr. Bento Teobaldo Ferraz 271