Three-point galaxy-galaxy lensing as a probe of dark matter halo shapes

Understand

We propose a method to measure the ellipticities of dark matter halos using the lens-shear-shear 3-point correlation function.

• This method is immune to effects of galaxy-halo misalignments that can potentially limit 2-point galaxy-galaxy lensing measurements of halo anisotropy.
• Using a simple model for the projected mass distributions of dark matter halos, we construct an ellipticity estimator that sums over all possible triangular configurations of the 3-point function.
• By applying our estimator to halos from N-body simulations, we find that systematic errors in the recovered ellipticity will be at the <5% fractional level.