Luminous Red Galaxy Halo Density Field Reconstruction and Application to Large Scale Structure Measurements

TL;DR

This paper presents a method to reconstruct the halo density field from galaxy surveys by removing nonlinear satellite galaxy effects, significantly improving the accuracy of large-scale structure measurements and cosmological constraints.

Contribution

The authors introduce a halo-based reconstruction technique that reduces nonlinear distortions, leading to more precise matter power spectrum estimates from galaxy surveys.

Findings

Reconstructed halo density field matches the underlying matter power spectrum within 1% for k<0.1 h/Mpc.

The method reduces bias in redshift space distortion measurements caused by Fingers-of-God effects.

Compared to previous aggressive FOG compression, our approach maintains better fidelity to the true matter distribution.

Abstract

The complex relationship between the galaxy density field and the underlying matter field limits our ability to extract cosmological constraints from galaxy redshift surveys. Our approach is to use halos rather than galaxies to trace the underlying mass distribution. We identify Fingers-of-God (FOGs) and replace multiple galaxies in each FOG with a single halo object. This removes the nonlinear contributions of satellite galaxies, the one-halo term. We test our method on a large set of high-fidelity mock SDSS Luminous Red Galaxy (LRG) catalogs. We find that the aggressive FOG compression algorithm adopted in the LRG P(k) analysis of Tegmark et al. (2006) leads to a ~10% correction to the underlying matter power spectrum at k = 0.1 h/Mpc and ~40% correction at k=0.2 h/Mpc, thereby compromising the cosmological constraints. In contrast, the power spectrum of our reconstructed halo density field deviates from the underlying matter power spectrum by less than 1% for k less than 0.1 h/Mpc and less than 4% for k less than 0.2 h/Mpc. The reconstructed halo density field also removes the bias in the measurement of the redshift space distortion parameter beta induced by the FOG smearing of the linear redshift space distortions.