Evidence for an Intermediate-mass Milky Way from Gaia DR2 Halo Globular Cluster Motions

By L. Watkins, R. P. van der Marel, S. Sohn, N. Evans II. Astrophysical Journal, 2018

151 citations recorded by the source corpus.

We estimate the mass of the Milky Way (MW) within 21.1 kpc using the kinematics of halo globular clusters (GCs) determined by Gaia. The second Gaia data release (DR2) contained a catalog of absolute proper motions (PMs) for a set of Galactic GCs and satellite galaxies. We select from the catalog only halo GCs, identifying a total of 34 GCs spanning , and use their 3D kinematics to estimate the anisotropy over this range to be , in good agreement with, though slightly lower than, a recent estimate for a sample of halo GCs using Hubble Space Telescope (HST) PM measurements further out in the halo. We then use the Gaia kinematics to estimate the mass of the MW inside the outermost GC to be , which corresponds to a circular velocity at of The implied virial mass is . The error bars encompass the uncertainties on the anisotropy and on the density profile of the MW dark halo, and the scatter inherent in the mass estimator we use. We get improved estimates when we combine the Gaia and HST samples to provide kinematics for 46 GCs out to 39.5 kpc: , , and . We show that these results are robust to potential substructure in the halo GC distribution. While a wide range of MW virial masses have been advocated in the literature, from below 1012 to above 2 × 1012 , these new data imply that an intermediate mass is most likely.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/26ae88e516084d12674465063861302676ad13c4

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Instrumentation

Citations in the corpus

The milky way total mass profile as inferred from Gaia DR2 (2019, background): “The model also agrees well with the mass measurements by Posti & Helmi (2019) and Watkins et al. (2019).”
The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2 (2018, background): “A higher MW mass of 1.8 × 1012 (e.g. Watkins et al. 2019) reduces the median pericentre to ∼25+13−9 kpc, which is around the lower limit of the pericentre uncertainties found for the orbits in a lighter MW (see, however, van der Marel & Guhathakurta 2008, for a possible bias towards larger…”
The Circular Velocity Curve of the Milky Way from 5 to 25 kpc (2018, methodology): “However, virial mass measurements that agree well with our estimate are presented by Bovy et al. (2012), as well as Eadie & Harris (2016) and Eadie & Jurić (2018), whose analyses are similar to the one from Watkins et al. (2018) and also based on kinematic data of globular clusters.”