Dynamical mass estimates of large-scale filaments in redshift surveys

We propose a new method to measure the mass of large-scale filaments in galaxy redshift surveys. The method is based on the fact that the mass per unit length of isothermal filaments depends only on their transverse velocity dispersion. Filaments that lie perpendicular to the line of sight may therefore have their mass per unit length measured from their thickness in redshift space. We present preliminary tests of the method and find that it predicts the mass per unit length of filaments in an N-body simulation to an accuracy of ∼35%. Applying the method to a select region of the Perseus-Pisces supercluster yields a mass-to-light ratio of M/L_B ≈ 450 h in solar units to within a factor of 2. The method measures the mass-to-light ratio on mass scales up to 10 times that of clusters of galaxies and could thereby yield new information on the behavior of the dark matter on large scales.