On the mass to light ratios of dwarf spheroidal galaxies

Previous estimates of the mass to light ratios of local dwarf spheroidal galaxies have indicated they form an inhomogeneous population. We here use a tidal equation and show that if we assume that all of these dwarf galaxies are on essentially similar orbits around the Milky Way (rather than having perigalactica comparable with their present distances) we can derive values of M/Lv which have a much smaller spread and no longer have correlations with luminosity and distance. It is then possible to maintain the view that either all of these dwarf galaxies contain dark matter or none of them do, with the main determining factor being the currently uncertain mass of the Milky Way. (author). 23 refs, 2 tabs