Evidence for an Intermediate-mass Milky Way from Gaia DR2 Halo Globular Cluster Motions
Open accessAbstract
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 10 12 to above 2 × 10 12 , these new data imply that an intermediate mass is most likely.
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References 76 · Cited by 189
Research works printed but not linked: 6
- Astropy Collaboration, Price-Whelan, A. M., Sipócz, B. M., et al. 2018, AJ, 156, 123 · DOI
- Binney, J., & Tremaine, S. 2008, Galactic Dynamics (2nd ed.; Princeton, NJ: Princeton Univ. Press)
- Eadie, G., & Jurić, M. 2018, arXiv:1810.10036 · arXiv
- Harris, W. E. 2001, in Star Clusters (Berlin: Springer), 223
- Sohn, S. T., Watkins, L. L., Fardal, M. A., et al. 2018, ApJ, 862, 52 · DOI
- Zinn, R. 1993, in ASP Conf. Ser. 48, Proc. XI Santa Cruz Summer Workshop in Astronomy and Astrophysics, The Globular Clusters-galaxy Connection, ed. G. H. Smith & J. P. Brodie (San Francisco, CA: ASP), 38
- Authors
- Watkins, L. L., van der Marel, R. P., Sohn, S. T., & Wyn Evans, N.
- Affiliations
- Space Telescope Science Institute (US)
- Corresponding author
- Watkins, Laura L.
- Venue
- The Astrophysical Journal
- Publisher
- American Astronomical Society
- Published
- 2019-03-12
- Volume
- 873
- Issue
- 2
- Pages
- 118
- ISSN
- 0004-637X (ISSN-L)
- 1538-4357
- OpenAlex
- W2799161332
- Cited by
- 189
- References
- 76
- Citations by year
- 2026: 9 · 2025: 17 · 2024: 23 · 2023: 11 · 2022: 19 · 2021: 18 · 2020: 42 · 2019: 39 · 2018: 11
- FWCI
- 15.47
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Licence
- Locations
- The Astrophysical Journal (publishedVersion)
- arXiv (Cornell University) (acceptedVersion)
- Apollo (University of Cambridge) (submittedVersion)
- arXiv (Cornell University)
- Apollo
- Funders
- National Aeronautics and Space Administration (NAS 526555, GO-14235, 526555)
- Space Telescope Science Institute (NAS5- 26555, 5-26555, 26555)
- European Space Agency (NAS 5-26555)
- Science and Technology Facilities Council (ST/N000927/1)
- Topics
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Galaxies: Formation, Evolution, Phenomena
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Cosmology and Gravitation Theories
- Keywords
- Milky Way mass, halo globular clusters, cluster kinematics, anisotropy, virial mass, circular velocity, Gaia DR2, satellite galaxies, halo substructure
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