Halo-Galaxy Lensing: A Full Sky Approach

Understand

The halo-galaxy lensing correlation function or the average tangential shear profile over sampled halos is a very powerful means of measuring the halo masses, the mass profile, and the halo-mass correlation function of very large separations in the linear regime.

• We reformulate the halo-galaxy lensing correlation in harmonic space.
• We find that, counter-intuitively, errors in the conventionally used flat-sky approximation remain at a % level even at very small angles.
• The errors increase at larger angles and for lensing halos at lower redshifts: the effect is at a few % level at the baryonic acoustic oscillation scales for lensing halos of $z\sim 0.2$, and comparable with the effect of primordial non-Gaussianity with $f_{\rm NL}\sim 10$ at large separations.