A Galaxy-weighted Measure of the Relative Peculiar-Velocity Dispersion

摘要

The relative pair dispersion of galaxies has for the past decade been the standard measure of the thermal energy of fluctuations in the observed galaxy distribution. This statistic is known to be unstable, since it is a pair-weighted measure that is very sensitive to rare, rich clusters of galaxies. As a more stable alternative, we present here a single-particleweighted statistic σ_1, which can be considered as an estimate of the one-dimensional rms peculiar-velocity dispersion of galaxies relative to their neighbors and which can be interpreted by means of a filtered version of the cosmic energy equation.