Cross-Correlating

Galaxy surveys probe both structure formation and the expansion rate, making them promising avenues for understanding the dark universe. Photometric surveys accurately map the 2D distribution of galaxy positions and shapes in a given redshift range, while spectroscopic surveys provide sparser 3D maps of the galaxy distribution. In this talk, I will present a way to analyse overlapping 2D and 3D maps jointly and without loss of information. One powerful application is the ability to simultaneously constrain the redshift distribution of the photometric sample, the sample biases, and cosmological parameters. I will show that combined analysis of DESI and LSST can improve cosmological constraints by factors of ~1.2 to ~1.8 on the region where they overlap relative to identically sized disjoint regions, while cross-correlating DES and SDSS-III in Stripe 82 improves photo-z parameter constraints by factors of ~2 to ~12 over internal photo-z reconstructions.