Constraining the Baryon-Dark Matter Relative Velocity with the Large-Scale 3-Point Correlation Function of the SDSS BOSS DR12 CMASS Galaxies

TL;DR

This paper investigates the impact of baryon-dark matter relative velocity on galaxy clustering, finding no significant bias and setting stringent limits that support the robustness of BAO measurements for cosmic distance estimation.

Contribution

It provides the most stringent constraint to date on the baryon-dark matter relative velocity bias using the SDSS BOSS DR12 CMASS galaxy data.

Findings

No significant detection of velocity bias ($b_v < 0.01$).

Bias could cause at most 0.3% systematic shift in BAO distance measurements.

Supports the robustness of upcoming surveys like DESI against this systematic.

Abstract

We search for a galaxy clustering bias due to a modulation of galaxy number with the baryon-dark matter relative velocity resulting from recombination-era physics. We find no detected signal and place the constraint $b_v < 0.01$ on the relative velocity bias for the CMASS galaxies. This bias is an important potential systematic of Baryon Acoustic Oscillation (BAO) method measurements of the cosmic distance scale using the 2-point clustering. Our limit on the relative velocity bias indicates a systematic shift of no more than $0.3\%$ rms in the distance scale inferred from the BAO feature in the BOSS 2-point clustering, well below the $1\%$ statistical error of this measurement. This constraint is the most stringent currently available and has important implications for the ability of upcoming large-scale structure surveys such as DESI to self-protect against the relative velocity as a possible systematic.