A Lower Limit on the Mass of Our Galaxy from the H3 Survey

Dennis Zaritsky, Charlie Conroy, Huanian Zhang, Rohan P. Naidu, Ana Bonaca, Nelson Caldwell, Phillip A. Cargile, Benjamin D. Johnson

Research output: Contribution to journalReview articlepeer-review

12 Scopus citations


The timing argument provides a lower limit on the mass of the Milky Way. Using a sample of 32 stars at R > 60 kpc drawn from the H3 Spectroscopic Survey and mock catalogs created from published numerical simulations, we find that M 200 > 0.91 1012 M o with 90% confidence. We recommend using this limit to refine the allowed prior mass range in more complex and sophisticated statistical treatments of Milky Way dynamics. The use of such a prior would have significantly reduced many previously published uncertainty ranges. Our analysis suggests that the most likely value of M 200 is ≈1.5 1012 M o, but establishing this as the Milky Way mass requires a larger sample of outer halo stars and a more complete analysis of the inner halo stars in H3. The imminent growth in the sample of outer halo stars due to ongoing and planned surveys will make this possible.

Original languageEnglish (US)
Article number114
JournalAstrophysical Journal
Issue number2
StatePublished - Jan 10 2020

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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