Action Model of Infall into the Virgo Cluster
  The observed infall of galaxies into the Virgo Cluster puts strong constraints on the mass of the cluster. A non-parametric fully non-linear description of the infall can be made with orbit reconstructions based on Numerical Action Methods. The mass of the cluster is determined to be $1.2 \times 10^{15} M_{\odot}$. The mass-to-light ratio for the cluster is found to be seven times higher than the mean ratio found across the region within V=3000 km/s. 
Brent Tully (Hawaii, Nice) and Roya Mohayaee (Nice)