Intrinsic alignment contamination to CMB lensing–galaxy weak lensing correlations from tidal torquing

摘要: Correlations of galaxy ellipticities with large-scale structure, due to galactic tidal interactions, provide a potentially significant contaminant measurements cosmic shear. However, these intrinsic alignments are still poorly understood for galaxies at the redshifts typically used in shear analyses. For spiral galaxies, it is thought that torquing determining resulting zero correlation between ellipticity and gravitational potential linear theory. Here, we calculate leading-order correction this result tidal-torque model from non-linear evolution, using second-order perturbation theory, relate contamination recently-measured cross-correlation CMB lensing potential. On scales relevant observations, squeezed limit bispectrum dominates correlation. Physically, mode sources modulates small-scale power hence ellipticity, evolution. We find angular has very similar scale dependence as alignment model, believed be appropriate elliptical galaxies. The amplitude predicted depend strongly on formation redshift, being smaller formed higher redshift when was smaller. Finally, make simple forecasts constraints forthcoming current measurements. note variance can significantly reduced difference if separated (e.g., colour).