Dane Noelle Cross and Carles Sánchez published a paper titled Inverse Galaxy-Galaxy Lensing: Magnification, Intrinsic Alignments and Cosmology .

The paper discusses how current and upcoming imaging galaxy surveys are extending galaxy samples to higher redshifts. This trend is particularly notable for lens galaxies, where only galaxy positions (not shapes) are needed. As a result, lens galaxies may frequently be observed at redshifts higher than those of source galaxies, changing the traditional galaxy-galaxy lensing configuration. In this paper, the authors explore where lens galaxies are behind source galaxies, and demonstrate how it is possible to tease out systematic error and better constrain cosmology.