A New Statistic for Redshift Surveys: the Redshift Dispersion of Galaxies

Abstract

We present a new statistic-the redshift dispersion-- which may prove useful for comparing next generation redshift surveys (e.g., the Sloan Digital Sky Survey) and cosmological simulations. Our statistic is specifically designed for the projection of phase space which is directly measured by redshift surveys. We find that the redshift dispersion of galaxies as a function of the projected overdensity has a strong dependence on the cosmological density parameter Omega. The redshift dispersion statistic is easy to compute and can be motivated by applying the Cosmic Virial Theorem to subsets of galaxies with the same local density. We show that the velocity dispersion of particles in these subsets is proportional to the product of Omega and the local density. Low resolution N-body simulations of several cosmological models (open/closed CDM, CDM+Lambda, HDM) indicate that the proportionality between velocity dispersion, local density and Omega holds over redshift scales in the range 50 km/s to 500 km/s. The redshift dispersion may provide an interesting means for comparing volume-limited subsamples of the Sloan Digital Sky Survey to equivalent N-body/hydrodynamics simulations.

LaTex 27 pages, 8 Postscript figures, added one figure and some changes to the text

References in corpus (1)

• A Reanalysis of Small Scale Velocity Dispersion in the CfA1 Survey

Cited by in corpus (17)

• Peculiar velocities of galaxies and clusters
• Maximum-Likelihood Comparisons of Tully-Fisher and Redshift Data. II. Results from an Expanded Sample
• The Real Space Power Spectrum of the PSCz Survey from 0.01 to 300 h/Mpc
• Locally Biased Galaxy Formation and Large Scale Structure
• A Galaxy-Weighted Measure of the Relative Peculiar Velocity Dispersion
• A Determination of the Hubble Constant from Cepheid Distances and a Model of the Local Peculiar Velocity Field
• Modeling peculiar velocities of dark matter halos
• The Galaxy Pairwise Velocity Dispersion as a Function of Local Density
• Quasar Clustering and Spacetime Geometry
• On the streaming model for redshift-space distortions
• The Pairwise Velocity Distribution Function of Galaxies in the LCRS, 2dF, and SDSS Redshift Surveys
• The Scaling of the Redshift Power Spectrum: Observations from the Las Campanas Redshift Survey
• The Galaxy-Weighted Small-Scale Velocity Dispersion of the Las Campanas Redshift Survey
• Cosmic Mach Number as a Function of Overdensity and Galaxy Age
• Nonlinear Velocity-Density Coupling: Analysis by Second-Order Perturbation Theory
• Numerical study of the cosmological velocity field as a function of density
• Numerical Analyses of Weakly Nonlinear Velocity-Density Coupling