Measuring gravitational lensing of the cosmic microwave background using cross correlation with large scale structure

TL;DR

This paper measures the gravitational lensing of the cosmic microwave background by cross-correlating WMAP data with NVSS galaxy distribution, achieving significant detection and forecasting future constraints.

Contribution

It introduces a quadratic estimator technique with full covariance filtering to detect and analyze the lensing-galaxy cross-correlation using WMAP and NVSS data.

Findings

Detection significance >3σ for lensing-galaxy correlation

Cross-power spectra pass null and diagnostic tests

Forecasts improved constraints with Planck and NVSS

Abstract

We cross correlate the gravitational lensing map extracted from cosmic microwave background measurements by the Wilkinson Microwave Anisotropy Probe (WMAP) with the radio galaxy distribution from the NRAO VLA Sky Survey (NVSS) by using a quadratic estimator technique. We use the full covariance matrix to filter the data, and calculate the cross-power spectra for the lensing-galaxy correlation. We explore the impact of changing the values of cosmological parameters on the lensing reconstruction, and obtain statistical detection significances at $>3\sigma$. The results of all cross correlations pass the curl null test as well as a complementary diagnostic test using the NVSS data in equatorial coordinates. We forecast the potential for Planck and NVSS to constrain the lensing-galaxy cross correlation as well as the galaxy bias. The lensing-galaxy cross-power spectra are found to be Gaussian distributed.