Correlation Lengths of Red and Blue Galaxies: A New Cosmic Ruler

TL;DR

This paper proposes a new cosmic ruler based on the nearly constant correlation length of red and blue galaxies across a range of redshifts, providing a bias-free measure of cosmic scales.

Contribution

It introduces a novel method using galaxy correlation lengths as a cosmic ruler, validated with SDSS data, to test cosmological models.

Findings

Correlation length remains nearly constant at ~4.8 Mpc/h from redshift 0 to 0.5.

Cluster number density remains stable over the same redshift range.

Provides a bias-free method for measuring cosmic length scales.

Abstract

A comparison of the correlation lengths of red galaxies with blue can provide a new cosmic ruler. Using 269,000 galaxies from the SDSS DR6 survey, I show that the 3D correlation length averaged over many clusters remains very nearly constant at Lo=4.797+/-0.024 Mpc/h from small redshifts out to redshifts of 0.5. This serves as a new measure of cosmic length scales as well as a means of testing the standard cosmological model that is almost free of selection biases. The cluster number density also appears to remain constant over this redshift range.