Dark Energy Survey Year 3 results: Exploiting small-scale information with lensing shear ratios

Using the first three years of data from Dark Energy Survey, we use ratios small-scale galaxy-galaxy lensing measurements around same lens sample to constrain source redshift uncertainties, intrinsic alignments and other nuisance parameters our model. Instead using a simple geometric approach for ratios, full modeling measurements, including corresponding integration over power spectrum contributions magnification. We perform extensive testing shear ratio (SR) by studying impact different effects such as inclusion baryonic physics, non-linear biasing, halo occupation distribution descriptions magnification, among others, realistic $N$-body simulations. validate robustness constraints in two independent samples, deriving large-scale which is simpler. The DES Y3 results demonstrate how provide significant improvements constraining several model, especially on calibration (IA). For redshifts, SR improves prior up 38\% some bins. Such improvements, it provides IA, translate tighter cosmological when combined with cosmic 2pt functions. In particular, data, $S_8$ 31\%, combination probes (3$\times$2pt) 10\%. presented this work are used an additional likelihood shear, 2$\times$2pt 3$\times$2pt fiducial analysis.