Galaxy redshift distributions are a very important ingredient for weak gravitational lensing analyses, and systematic errors in their measurement propagate to constraints on dark matter and dark energy. Most weak lensing galaxy surveys focus on getting good quality photometric imaging rather than getting spectroscopic information for all the galaxies in the sample. Photometric redshift estimation methods are inherently lower-resolution than spectroscopic redshift estimation. In this paper, we use measurements of the angular clustering between photometric and spectroscopic galaxy surveys that spatially overlap on the sky to investigate the accuracy of the photometric galaxy redshift distributions. We find evidence that the given photometric galaxy redshift distributions are biased relative to the true underlying distributions. For the surveys considered in this work, the resulting error on cosmology constraints is fairly small, although one can imagine that the level of impact will become much more important as statistical errors decrease with future survey data.
Choi, A., Heymans, C., Blake, C., et al. 2016, MNRAS, 463, 3737