Antibiasing: High Mass-to-Light Ratios in Dense Clusters
  Modeling of the velocity field of the Local Supercluster leads to the conclusion that there must be a substantial differential between the mass-to-light ratios of most galaxies and those in a small number of special places. Specifically, M/L=1000 is indicated for the full Virgo Cluster while M/L=150 is appropriate for most environments. It is argued that a higher M/L value is characteristic of E/S0 knots, regions where the galaxy density is high and collapse time scales are short. Regions larger than galaxies where collapse is ocurring only on the order of the age of the universe, the environment where spirals and irregulars predominate, are characterized by a low M/L. Overall, the mean density of the universe is well below closure. There could be comparable total mass in the relatively rare E/S0 knots as there is in the environments dominated by spirals and irregulars. 
R. Brent Tully and Edward J. Shaya