The galaxy-galaxy lensing contribution to the cosmic shear two-point function

We note that galaxy-galaxy lensing by nonspherical galaxy halos produces a net anticorrelation between the shear of background galaxies and the ellipticity of foreground galaxies. This anticorrelation would contaminate the tomographic cosmological weak lensing two-point function if the effect were not taken into account. We compare the size of the galaxy-galaxy lensing contribution to the change in the cosmic shear two-point cross-correlation function due to a change in the dark energy equation of state w of 1%. We find them comparable on scales less than or similar to 5' for NFW galaxy profiles, and out to much larger scales for SIE profiles. However, the galaxy-galaxy lensing signal has a characteristic spatial and redshift pattern that should allow it to be removed.