An improved mass determination for M31 from its satellite galaxies

Patrick Côté, Mario Mateo, W. L.W. Sargent, Edward W. Olszewski

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


The High-Resolution Echelle Spectrometer on the Keck I telescope has been used to measure the first radial velocities for stars belonging to the Andromeda I and III dwarf spheroidal galaxies. Our radial velocity for And III matches that reported by Blitz & Robishaw for an adjacent H I gas complex, supporting the association of this galaxy with a high-velocity cloud. New and previously published radial velocities for a sample of confirmed or suspected M31 satellites are combined with a homogeneous set of distance estimates to calculate the total mass of M31. Assuming the satellite orbits are isotropic, we find a median mass of MA ≃ (7.9 ± 0.5) × 1011 M from eight candidate satellites having deprojected distances from M31 in excess of RA ≃ 100 kpc. If the orbits are radial, the inferred mass increases to MA ≃ (21.5 ± 3.8) × 1011 M for circular orbits, the enclosed mass is MA ≃ (3.7 ± 0.4) × 1011 M. These masses are somewhat lower than those found for luminous spiral galaxies based on the ensemble dynamics of the their satellites, although the estimates are nevertheless consistent given the large uncertainties.

Original languageEnglish (US)
Pages (from-to)L91-L94
JournalAstrophysical Journal
Issue number2 PART 2
StatePublished - Jul 10 2000


  • Galaxies: halos
  • Galaxies: individual (M31)
  • Galaxies: kinematics and dynamics
  • Galaxies: spiral
  • Intergalactic medium

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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