Dwarf spheroidal galaxies and non-Newtonian gravity

Ortwin E. Gerhard, David N. Spergel

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44 Scopus citations


We derive a virial theorem and an analog for King's formula in modified Newtonian dynamics (MOND; Milgrom 1983) and use these to estimate the mass-to-light ratios (M/Ls) in MOND of the dwarf spheroidal galaxies in the Local Group. We find that the low-velocity dispersion observed in the Fornax dwarf galaxy implies low values for its M/L in MOND: 0.3-1. In particular the derived value in the core of Fornax (0.3) is much lower than expected for a normal old stellar population. Conversely, the velocity-dispersion measurements in Draco and Ursa Minor appear to still require dark matter in MOND. We show that M/L must vary between the dwarf spheroidals around the Galaxy by a factor of order at least 20, even in MOND.

Original languageEnglish (US)
Pages (from-to)38-43
Number of pages6
JournalAstrophysical Journal
Issue number1
StatePublished - 1992

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Dark matter
  • Galaxies: elliptical and lenticular, cD
  • Galaxies: kinematics and dynamics
  • Gravitation


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