Dwarf Spheroidal Galaxies and Non-Newtonian Gravity
Abstract
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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 1992
- DOI:
- 10.1086/171763
- Bibcode:
- 1992ApJ...397...38G
- Keywords:
-
- Dark Matter;
- Dwarf Galaxies;
- Elliptical Galaxies;
- Galactic Clusters;
- Mass To Light Ratios;
- Galactic Evolution;
- Gravitation Theory;
- Kinematics;
- Metallicity;
- Astrophysics;
- COSMOLOGY: DARK MATTER;
- GALAXIES: ELLIPTICAL AND LENTICULAR;
- CD;
- GALAXIES: KINEMATICS AND DYNAMICS;
- GRAVITATION