On the signature of the baryon-dark matter relative velocity in the two and three-point galaxy correlation functions

Understand

We develop a configuration-space picture of the relative velocity between baryons and dark matter that clearly explains how it can shift the BAO scale in the galaxy-galaxy correlation function.

• The shift occurs because the relative velocity is non-zero only within the sound horizon and thus adds to the correlation function asymmetrically about the BAO peak.
• We further show that in configuration space the relative velocity has a localized, distinctive signature in the three-point galaxy correlation function (3PCF).
• In particular, we find that a multipole decomposition is a favorable way to isolate the relative velocity in the 3PCF, and that there is a strong signature in the l=1 multipole for triangles with 2 sides around the BAO scale.