Intrinsic alignment as an RSD contaminant in the DESI survey

We measure the tidal alignment of major axes Luminous Red Galaxies (LRGs) from Legacy Imaging Survey and use it to infer artificial redshift-space distortion signature that will arise an orientation-dependent, surface-brightness selection in Dark Energy Spectroscopic Instrument (DESI) survey. Using photometric redshifts down-weight shape-density correlations due weak lensing, we intrinsic LRGs. Separately, estimate net polarization LRG orientations DESI's fiber-magnitude target be order 10^-2 along line sight. these measurements a linear model, forecast 0.5% fractional decrease on quadrupole 2-point correlation function for projected separations 40-80 Mpc/h. also halo catalog Abacus Summit cosmological simulation suite reproduce this false quadrupole.