Abstract:

We develop a configuration-space picture of the relative velocitybetween baryons and dark matter that clearly explains how it can shiftthe BAO scale in the galaxy-galaxy correlation function. The shiftoccurs because the relative velocity is non-zero only within the soundhorizon and thus adds to the correlation function asymmetrically aboutthe BAO peak. We further show that in configuration space the relativevelocity has a localized, distinctive signature in the three-pointgalaxy correlation function (3PCF). In particular, we find that amultipole decomposition is a favorable way to isolate the relativevelocity in the 3PCF, and that there is a strong signature in the l=1multipole for triangles with 2 sides around the BAO scale. Finally, weinvestigate a further compression of the 3PCF to a function of only onetriangle side that preserves the localized nature of the relativevelocity signature while also nicely separating linear from non-linearbias. We expect that this scheme will substantially lessen thecomputational burden of finding the relative velocity in the 3PCF. Therelative velocity's 3PCF signature can be used to correct the shiftinduced in the galaxy-galaxy correlation function so that no systematicerror due to this effect is introduced into the BAO as used forprecision cosmology.

Notes:

20 pages, 12 figures, submitted MNRAS

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