Mapping the real space distributions of galaxies in SDSS DR7: I. Two Point Correlation Functions

TL;DR

This study reconstructs the real space galaxy distribution in SDSS DR7 using a novel RSD correction method, enabling detailed analysis of the two-point correlation function and galaxy clustering properties.

Contribution

It introduces a new method for correcting redshift space distortions at the individual galaxy level and applies it to SDSS DR7 data, providing more accurate clustering measurements.

Findings

Reconstructed real space 2PCF agrees with direct measurements within cosmic variance.

The Sloan Great Wall is less dominant in real space than in redshift space.

Clustering deviations from power-law and 1-halo to 2-halo transition are observed.

Abstract

Using a method to correct redshift space distortion (RSD) for individual galaxies, we mapped the real space distributions of galaxies in the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). We use an ensemble of mock catalogs to demonstrate the reliability of our method. Here as the first paper in a series, we mainly focus on the two point correlation function (2PCF) of galaxies. Overall the 2PCF measured in the reconstructed real space for galaxies brighter than $^{0.1}{\rm M}_r-5\log h=-19.0$ agrees with the direct measurement to an accuracy better than the measurement error due to cosmic variance, if the reconstruction uses the correct cosmology. Applying the method to the SDSS DR7, we construct a real space version of the main galaxy catalog, which contains 396,068 galaxies in the North Galactic Cap with redshifts in the range $0.01 \leq z \leq 0.12$. The Sloan Great Wall, the largest known structure in the nearby Universe, is not as dominant an over-dense structure as appears to be in redshift space. We measure the 2PCFs in reconstructed real space for galaxies of different luminosities and colors. All of them show clear deviations from single power-law forms, and reveal clear transitions from 1-halo to 2-halo terms. A comparison with the corresponding 2PCFs in redshift space nicely demonstrates how RSDs boost the clustering power on large scales (by about $40-50\%$ at scales $\sim 10 h^{-1}{\rm {Mpc}}$) and suppress it on small scales (by about $70-80\%$ at a scale of $0.3 h^{-1}{\rm {Mpc}}$).