The Peculiar Velocity Correlation Function

TL;DR

This paper analyzes the peculiar velocity correlation function using observational data and simulations to estimate cosmological parameters, highlighting the challenges posed by cosmic variance and non-Gaussian uncertainties.

Contribution

It introduces a method to compare observed velocity correlations with theoretical models, providing constraints on cosmological parameters from peculiar velocity data.

Findings

Estimated cosmological parameters consistent with Planck results.

Large cosmic variance affects the reliability of velocity correlation as a large-scale structure probe.

Non-Gaussian distribution of uncertainties complicates analysis.

Abstract

We present an analysis of the two-point peculiar velocity correlation function using data from the CosmicFlows catalogues. The Millennium and MultiDark Planck 2 N-body simulations are used to estimate cosmic variance and uncertainties due to measurement errors. We compare the velocity correlation function to expectations from linear theory to constrain cosmological parameters. Using the maximum likelihood method, we find values of $\Omega_m= 0.315^{+0.205}_{-0.135}$ and $\sigma_8=0.92^{+0.440}_{-0.295}$, consistent with the Planck and Wilkinson Microwave Anisotropy Probe CMB derived estimates. However, we find that the cosmic variance of the correlation function is large and non-Gaussian distributed, making the peculiar velocity correlation function less than ideal as a probe of large-scale structure.