Cross-correlation Between Planck CMB Lensing Potential and HELP Galaxy Catalogues

Weak gravitational lensing of the Cosmic Microwave Background (CMB) contains information about the matter distribution in the Universe. Cross-correlation of CMB lensing with tracers of large scale structures like galaxies or quasars can be used to constrain the cosmological model of the Universe. We present the first study of the cross-correlation between Cosmic Microwave Background (CMB) lensing potential measured by the Planck satellite and z≥ 0.8 galaxies from the Herschel Extragalactic Legacy Project (HELP) photometric redshift catalogues. We use Maximum Likelihood Estimation to measure the galaxy linear bias, b, and the amplitude of cross-correlation, A, from a joint analysis of cross-power spectrum and galaxy auto-power spectrum. We find the amplitude A to be consistently lower than the expected value of unity for the standard cosmological model. We explore various tests and systematics to account for the observed discrepancy in the amplitude of cross-correlation.