# Velocity-Density Correlations from the cosmicflows-3 Distance Catalog and the 2MASS Redshift Survey

## TL;DR

This paper measures the correlation between galaxy peculiar velocities and mass density dipoles, providing constraints on cosmological parameters consistent with the standard model, and demonstrating the potential of velocity-density correlation studies.

## Contribution

First measurement of velocity-density dipole correlation using cosmicflows-3 and 2MRS data, offering new constraints on cosmological parameters within the standard model.

## Key findings

- Correlation detected at >4σ confidence level.
- Results consistent with ΛCDM model within 1.7σ.
- Derived constraints on Ω^{0.55}σ_8 and galaxy bias factor.

## Abstract

The peculiar velocity of a mass tracer is on average aligned with the dipole modulation of the surrounding mass density field. We present a first measurement of the correlation between radial peculiar velocities of objects in the cosmicflows-3 catalog and the dipole moment of the 2MRS galaxy distribution in concentric spherical shells centered on these objects. Limiting the analysis to cosmicflows-3 objects with distances of $100 \rm Mpc h^{-1}$, the correlation function is detected at a confidence level $> 4\sigma$. The measurement is found consistent with the standard $\Lambda$CDM model at $< 1.7\sigma$ level. We formally derive the constraints $0.32<\Omega^{0.55}\sigma_8<0.48$ ($68\% $ confidence level) or equivalently $0.34<\Omega^{0.55}/b<0.52$, where $b$ is the galaxy bias factor. Deeper and improved peculiar velocity catalogs will substantially reduce the uncertainties, allowing tighter constraints from this type of correlations.