Mass to light ratio

From Wikipedia, the free encyclopedia

In physical cosmology the mass to light ratio is the quotient between the total mass of a galaxy or a cluster and its luminosity. These ratios are often reported using the value calculated for the sun as a baseline ratio. The mass to light ratios of galaxies and clusters are all much greater than that of the sun due in part to the fact that most of the matter in these objects do not reside within stars and observations suggest that a large fraction is present in the form of dark matter.

Masses are often calculated from the dynamics of the virialized system or from gravitational lensing. Luminosities are obtained from photometric observations and correcting the observed brightness of the object for the distance dimming effects.