The mass distribution and gravitational potential of the Milky Way

By P. McMillan. 2016

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We present mass models of the Milky Way created to fit observational constraints and to be consistent with expectations from theoretical modelling. The method used to create these models is that demonstrated in our previous study, and we improve on those models by adding gas discs to the potential, considering the effects of allowing the inner slope of the halo density profile to vary, and including new observations of maser sources in the Milky Way amongst the new constraints. We provide a best-fitting model, as well as estimates of the properties of the Milky Way. Under the assumptions in our main model, we find that the Sun is R0 = 8.20 ± 0.09 kpc from the Galactic Centre, with the circular speed at the Sun being v0 = 232.8 ± 3.0 kms-1; and that the Galaxy has a total stellar mass of (54.3 ± 5.7) × 109 M⊙, a total virial mass of (1.30 ± 0.30) × 1012M⊙ and a local dark-matter density of 0.40 ± 0.04 GeV cm-3, where the quoted uncertainties are statistical. These values are sensitive to our choice of priors and constraints. We investigate systematic uncertainties, which in some cases may be larger. For example, if we weaken our prior on R0, we find it to be 7.97 ± 0.15 kpc and that v0 = 226.8 ± 4.2 kms-1.We find that most of these properties, including the local dark-matter density, are remarkably insensitive to the assumed power-law density slope at the centre of the dark-matter halo. We find that it is unlikely that the local standard of rest differs significantly from that found under assumptions of axisymmetry. We have made code to compute the force from our potential, and to integrate orbits within it, publicly available. (Less)

Subfields: Astronomy and Astrophysics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/b9ab001ef8add0c2459cc627cf319dedd59ddd86

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Citations in the corpus

The GALAH+ survey: Third data release (2020, methodology): “For our calculations we use the best fitting axisymmetric potential by McMillan (2017) with a Solar radius of 8.21 kpc, consistent with the latest measurement by Gravity Collaboration et al. (2019) of 8.178 ± 0.013stat.”
Proper motions and dynamics of the Milky Way globular cluster system fromGaiaDR2 (2018, methodology): “We allow the latter two to vary in a rather limited range, inspired by the best-fit potential suggested in McMillan (2017): Mbulge = 9 × 109 M , Mdisc = 5.5 × 1010 M , both with relative uncertainty of 10%.”
The milky way total mass profile as inferred from Gaia DR2 (2019, methodology): “We show that the contracted DM halo cannot be modelled as a pure NFW profile and even more flexible formulae, such as the generalised NFW profile (gNFW, which has been used to model the MW halo – McMillan 2017; Karukes et al. 2019), struggle to describe the radial profile of the contracted halo.”
Mean proper motions, space orbits, and velocity dispersion profiles of Galactic globular clusters derived fromGaiaDR2 data (2018, result): “As a check of the robustness of our results, we also calculated cluster orbits using the Milky Way models of Johnston, Spergel & Hernquist (1995) and the best-fitting model of McMillan (2017), but found only little difference in the final results compared to the Irrgang et al. model.”
Formation of Double Neutron Star Systems (2017, methodology): “Finally, to convert the SSB velocity vector to the LSR we have used the Galactic model of McMillan (2017).”
Evidence for two early accretion events that built the Milky Way stellar halo (2019, methodology): “The potential used to represent the Milky Way is the one recommended as the best amongst the suite studied by McMillan (2017).”
First results from the IllustrisTNG simulations: a tale of two elements - chemical evolution of magnesium and europium (2017, methodology): “First, we select for galaxies with a total halo mass, M200,crit, in the range (0.6−2)×1012 M (Eadie et al. 2015; McMillan 2017; Zaritsky & Courtois 2017), which results in approximately 2000 galaxies.”
Gaia EDR3 view on galactic globular clusters (2021, methodology): “…properties of the entire population of globular clusters: semimajor axis, eccentricity and inclination, computed in two variants of static Milky Way potentials: McMillan (2017) or Bovy (2015) (these properties remain qualitatively similar if we use other reasonable choices for the potential).”
The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2 (2018, methodology): “We opt for a fixed time-independent axisymmetric Milky Way potential from McMillan (2017),4 place the dwarf at apocentre ∼13 Gyr ago and integrate forwards.”
Origin of the system of globular clusters in the Milky Way (2019, methodology): “We used the AGAMA package (Vasiliev 2019b) with the McMillan (2017) potential to compute GCs orbital parameters like the apocenter (apo), maximum height from the disc (Zmax), and eccentricity (ecc).”
Gravitational probes of dark matter physics (2017, background): “Because the efficiency of star formation drops rapidly with decreasing halo mass (Figure 4), the stellar halo of the Milky Way contributes only ∼ 1% of the total stellar mass of the Milky Way [125, 156].”