The M/L versus velocity dispersion

The dynamical mass-to-light (M/L) ratio and the strength of the higher order Balmer lines Hδ and Hγ versus the velocity dispersion of the galaxy. The M/L versus velocity dispersion relation is a representation of the Fundamental Plane. The solid blue line shows the best fit to the low-redshift samples (Coma, Perseus and A194), while the dot-dashed lines show models for formation redshifts dependent on the velocity dispersions, color-coded for each of the clusters. The M/L ratios are modeled reasonably well by these models. However, the strength of the Balmer lines is significantly weaker than expected from the models, indicating that the M/L ratios and the Balmer line measurements cannot be reconciled with a simple passive evolution model with a formation redshift depending on the galaxy velocity dispersion.