An observational signal of the void shape correlation and its link to the cosmic web

TL;DR

This paper detects and models the correlation of cosmic void shapes with large-scale tidal fields, providing observational evidence and potential for constraining cosmological parameters like neutrino mass.

Contribution

It presents the first clear observational detection of void shape correlations and links them to the large-scale tidal and velocity shear fields using SDSS data.

Findings

Detected 4 sigma correlation of void shapes at 20 Mpc/h

Established linear scaling of void shape correlation with density field

Observed cross-correlation between void shapes and velocity shear field

Abstract

The shapes of cosmic voids are prone to distortions by the external tidal forces since their low-densities imply a lower internal resistance. This susceptibility of the void shapes to the tidal distortions makes them useful as an indicator of the large-scale tidal and density fields, despite the practical difficulty in defining them. Using the void catalog constructed by Pan et al. (2012) from the Seventh Data Release of the Sloan Digital Sky Survey (SDSS DR7), we detect a clear 4 sigma signal of spatial correlations of the void shapes on the scale of 20 Mpc/h and show that the signal is robust against the projection of the void shapes onto the plane of sky. By constructing a simple analytic model for the void shape correlation, within the framework of tidal torque theory, we demonstrate that the void shape correlation function scales linearly with the two-point correlation function of the linear density field. We also find a direct observational evidence for the cross-correlation of the void shapes with the large-scale velocity shear field that was linearly reconstructed by Lee et al. (2014) from the SDSS DR7. We discuss the possibility of using the void shape correlation function to break the degeneracy between the density parameter and the power spectrum amplitude and to independently constrain the neutrino mass as well.