Applying the Halo Model to Large Scale Structure Measurements of the Luminous Red Galaxies: SDSS DR7 Preliminary Results

Abstract

The non-trivial relationship between observations of galaxy positions in redshift space and the underlying matter field complicates our ability to determine the linear theory power spectrum and extract cosmological information from galaxy surveys. The Sloan Digital Sky Survey (SDSS) Luminous Red Galaxy (LRG) catalog has the potential to place powerful constraints on cosmological parameters. LRGs are bright, highly biased tracers of large-scale structure. However, because they are highly biased, the non-linear contribution of satellite galaxies to the galaxy power spectrum is large and Fingers-of-God are significant. We propose an new approach to recovering the matter field from galaxy observations. Our approach is to use halos rather than galaxies to trace the underlying mass distribution. We identify Fingers-of-God (FOGs) and replace each FOG with a single halo object. This removes the nonlinear contribution of satellite galaxies, the one-halo term. We test our method on a large set of high-fidelity mock SDSS LRG catalogs and present consistency checks between the mock and LRG DR7 reconstructed halo density fields. We present preliminary cosmological constraints from the LRG DR7 reconstructed halo density field power spectrum. Finally, we summarize the potential gains in cosmological parameter constraints using our approach and the largest remaining sources of systematic errors.