Dark Energy Survey Year 3 Results: clustering redshifts – calibration of the weak lensing source redshift distributions with <i>redMaGiC</i> and BOSS/eBOSS

We present the calibration of Dark Energy Survey Year 3 (DES Y3) weak lensing source galaxy redshift distributions $n(z)$ from clustering measurements. In particular, we cross-correlate (WL) galaxies sample with redMaGiC (luminous red secure photometric redshifts) and a spectroscopic BOSS/eBOSS to estimate distribution DES sources sample. Two distinct methods for using statistics are described. The first uses information independently mean within window, as done in Y1 analysis. second method establishes likelihood data function $n(z)$, which can be incorporated into schemes generating samples subject combined constraints. Both incorporate marginalisation over various astrophysical systematics, including magnification redshift-dependent galaxy-matter bias. characterise uncertainties simulations; recovers $z$ tomographic bins RMS (precision) $\sim 0.014$. Use is shown vastly improve accuracy shape derived data. two then applied Y3