Cross-correlation of CFHTLenS galaxy catalogue and Planck CMB lensing using the halo model prescription

TL;DR

This study cross-correlates CFHTLenS galaxy data with Planck CMB lensing, improving covariance estimation with the halo model, validating with simulations, and providing refined galaxy bias and cross-correlation amplitude measurements.

Contribution

It introduces an analytic covariance calculation using the halo model and validates it with simulations, enhancing the analysis of galaxy-CMB lensing correlations.

Findings

Galaxy bias around 0.92 for both releases

Cross-correlation amplitude close to 1 for 2013 release

Confirmed differences between data releases are statistically compatible

Abstract

I cross-correlate the galaxy counts from the Canada-France Hawaii Telescope Lensing Survey (CFHTLenS) galaxy catalogue and Cosmic Microwave Background (CMB) convergence from the Planck data release 1 (2013) and 2 (2015), following the work of Omori & Holder (2015). I improve their study by computing an analytic covariance from the Halo Model, implementing simulations to validate the theoretically estimated error bars and the reconstruction method, fitting both a galaxy bias and a cross-correlation amplitude using the joint cross and galaxy auto-correlation, and performing a series of null tests. Using a bayesian analysis, I find a galaxy bias $b=0.92_{-0.02}^{+0.02}$ and a cross-correlation amplitude $A=0.85_{-0.16}^{+0.15}$ for the 2015 release, whereas for the 2013 release I find $b=0.93_{-0.02}^{+0.02}$ and $A=1.05_{-0.15}^{+0.15}$. I thus confirm the difference between the two releases found by Omori & Holder (2015), although both values of the amplitude now appear to be compatible with the fiducial value $A=1$.