Speaker
Description
Gravitational lensing of the cosmic microwave background is a powerful probe of the distribution of matter in the post-recombination Universe. Combining CMB lensing with galaxy surveys at different redshifts provides a tomographic view of the growth of structure, improving cosmological constraints. Using Planck CMB lensing and unWISE infrared galaxies, we find $S_8 \equiv \sigma_8 \sqrt{\Omega_m/0.3} = 0.784 \pm 0.015$. This result agrees well with $S_8$ measured from the weak lensing surveys DES and KiDS, and is 2.4-$\sigma$ below the Planck value. I will also discuss the prospects for constraining local primordial non-Gaussianity ($f_\textrm{NL}$) with CMB lensing cross-correlations, by measuring the scale-dependence of the galaxy bias on very large scales. Galaxy survey systematics can create spurious power at large scales in the auto-correlation, mimicking the scale-dependent bias signal and degrading the constraining power. Cross-correlations are cleaner than auto-correlations since systematics in each survey are not correlated, thus providing an alternative route to large-scale structure $f_\textrm{NL}$ constraints.
