Calibrating Photometric Redshifts using Cross-Correlations with Spectroscopy and the CMB
Abstract: Photometric cosmic surveys like the Dark Energy Survey (DES) are producing increasingly precise estimates of cosmological parameters. One of the largest sources of error in such surveys is the estimation of redshifts. While spectroscopy produces highly accurate redshifts, current spectroscopic surveys cannot probe large enough volumes or numbers of objects for comparable cosmological constraints. Instead, surveys like DES use "photometric redshift" algorithms, which can have considerable uncertainty, especially at fainter magnitudes.
In this talk, I will discuss work on two methods of estimating redshifts separate from photometry. For the DES year-1 dataset, we calibrated redshifts using the cross-correlations method, which involves galaxy-clustering measurements with a spectroscopic sample of galaxies. I will focus on the work calibrating the "redMaGiC" sample of luminous red galaxies used in multiple DES year-1 analyses. I will also briefly discuss the prospects of deriving redshift information from correlations of galaxy positions with cosmic microwave background (CMB) lensing measurements. Such analyses greatly improve with the next generation of CMB experiments.