3D Genus Topology of Luminous Red Galaxies

TL;DR

This study measures the 3D genus topology of large-scale structure using Luminous Red Galaxies from SDSS, confirming consistency with Gaussian initial conditions and demonstrating the potential for future cosmological measurements.

Contribution

It provides the first large-scale 3D topology measurement using LRGs, showing consistency with Gaussian initial conditions and validating modeling approaches with N-body simulations.

Findings

Topology is sponge-like and consistent with Gaussian random phase initial conditions.

Genus curve amplitude measured with 4% uncertainty.

N-body simulations accurately explain small distortions in the genus curve.

Abstract

We measure the 3D genus topology of large scale structure using Luminous Red Galaxies (LRGs) in the Sloan Digital Sky Survey and find it consistent with the Gaussian random phase initial conditions expected from the simplest scenarios of inflation. This studies 3D topology on the largest scales ever obtained. The topology is sponge-like. We measure topology in two volume-limited samples: a dense shallow sample studied with smoothing length of 21h^{-1}Mpc, and a sparse deep sample studied with a smoothing length of 34h^{-1}Mpc. The amplitude of the genus curve is measured with 4% uncertainty. Small distortions in the genus curve expected from non-linear biasing and gravitational effects are well explained (to about 1-\sigma accuracy) by N-body simulations using a subhalo-finding technique to locate LRGs. This suggests the formation of LRGs is a clean problem that can be modeled well without any free fitting parameters. This bodes well for using LRGs to measure the characteristic scales such as the baryon oscillation scale in future deep redshift surveys.