Constraining the baryon-dark matter relative velocity with the large-scale three-point correlation function of the SDSS BOSS DR12 CMASS galaxies

We search for a galaxy clustering bias due to a modulation of galaxynumber with the baryon-dark matter relative velocity resulting fromrecombination-era physics. We find no detected signal and place theconstraint b_v 0.01 on the relative velocity bias for theCMASS galaxies. This bias is an important potential systematic of baryonacoustic oscillation (BAO) method measurements of the cosmic distancescale using the two-point clustering. Our limit on the relative velocitybias indicates a systematic shift of no more than 0.3 per cent rms inthe distance scale inferred from the BAO feature in the BOSS two-pointclustering, well below the 1 per cent statistical error of thismeasurement. This constraint is the most stringent currently availableand has important implications for the ability of upcoming large-scalestructure surveys such as the Dark Energy Spectroscopic Instrument(DESI) to self-protect against the relative velocity as a possiblesystematic.