The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Effect of smoothing of density field on reconstruction and anisotropic BAO analysis

摘要

The reconstruction algorithm introduced by \cite{Eis07}, which is widely usedin clustering analysis, is based on the inference of the first order Lagrangiandisplacement field from the Gaussian smoothed galaxy density field in redshiftspace. The \modif2{smoothing scale} applied to the density field affects theinferred displacement field that is used to move {the galaxies}, and partially\modif2{erases} the nonlinear evolution {of the density field}. In this article, we explore this crucial step \modif2{in} the reconstructionalgorithm. We study the performance of the reconstruction technique using twometrics: first, we study the performance using the anisotropic clustering,extending previous studies focused on isotropic clustering; second, we studyits effect on the displacement field. We find that smoothing has a strongeffect in the quadrupole of the correlation function and affects the accuracyand precision \modif2{with} which we can measure $D_A (z)$ and $H(z)$. We findthat the optimal smoothing scale to use in the reconstruction algorithm appliedto BOSS-CMASS is between 5-10 $h^{-1}$Mpc. Varying from the "usual"15$h^{-1}$Mpc to $5 h^{-1}$Mpc \modif2{shows} $\sim$ 0.3\% variations in$D_A(z)$ and $\sim$ 0.4\% $H(z)$ and uncertainties are also reduced by 40\% and30\% respectively. We also find that the accuracy of velocity fieldreconstruction depends strongly on the smoothing scale used for the densityfield. We measure the bias and uncertainties associated with different choicesof smoothing length.