Beyond the classical distance-redshift test: cross-correlating redshift-free standard candles and sirens with redshift surveys

TL;DR

This paper introduces a multi-tracer Alcock-Paczynski test that cross-correlates redshift-free standard candles and gravitational wave sirens with galaxy surveys, offering a more effective alternative to traditional redshift-dependent methods for constraining dark energy.

Contribution

It presents a novel multi-tracer approach that combines redshift-free distance tracers with galaxy surveys, improving dark energy constraints without requiring spectroscopic redshifts.

Findings

Cross-correlating 50,000 supernovae with galaxy surveys outperforms traditional methods.

The approach is applicable to gravitational wave sirens and other redshift-free tracers.

Method enhances dark energy constraints without spectroscopic redshift measurements.

Abstract

LSST will supply up to $10^6$ supernovae (SNe) to constrain dark energy through the distance-redshift ($D_L$-$z$) test. Obtaining spectroscopic SN redshifts (spec-$z$s) is unfeasible; alternatives are suboptimal and may be biased. We propose a powerful multi-tracer generalization of the Alcock-Paczynski test that pairs redshift-free distance tracers and an overlapping galaxy redshift survey. Cross-correlating $5\times 10^4$ redshift-free SNe with DESI or Euclid outperforms the classical $D_L$-$z$ test with spec-$z$s for all SN. Our method also applies to gravitational wave sirens or any redshift-free distance tracer.