The clustering of the SDSS-IV extended Baryon Oscillation Spectroscopic Survey DR16 luminous red galaxy and emission line galaxy samples: cosmic distance and structure growth measurements using multiple tracers in configuration space

TL;DR

This paper presents a multi-tracer analysis of SDSS-IV eBOSS DR16 galaxy samples, measuring cosmic distances and growth rate with improved precision by combining LRG and ELG data in configuration space.

Contribution

It introduces a novel multi-tracer approach combining LRG and ELG samples for joint BAO and RSD measurements, enhancing statistical precision over single-tracer analyses.

Findings

Detected cross-correlation between LRG and ELG samples.

Measured growth rate fσ8=0.342±0.085 from cross sample.

Improved the Figure of Merit by 11% and reduced uncertainty in fσ8 by 11.6%.

Abstract

We perform a multi-tracer analysis using the complete Sloan Digital Sky Survey IV (SDSS-IV) extended Baryon Oscillation Spectroscopic Survey (eBOSS) DR16 luminous red galaxy (LRG) and the DR16 emission line galaxy (ELG) samples in the configuration space, and successfully detect a cross correlation between the two samples, and find the growth rate to be $f\sigma_8=0.342 \pm 0.085$ ($\sim25$ per cent accuracy) from the cross sample alone. We perform a joint measurement of the baryonic acoustic oscillation (BAO) and redshift space distortion (RSD) parameters at a single effective redshift of $z_{\rm eff}= 0.77$, using the auto- and cross-correlation functions of the LRG and ELG samples, and find that the comoving angular diameter distance $D_M(z_{\rm eff})/r_d = 18.85\pm 0.38$, the Hubble distance $D_H(z_{\rm eff})/r_d = 19.64 \pm 0.57$, and $f\sigma_8(z_{\rm eff}) = 0.432 \pm 0.038$, which is consistent with a $\Lambda$CDM model at $68\%$ CL. Compared to the single-tracer analysis on the LRG sample, the Figure of Merit (FoM) of $\alpha_{\perp}, \alpha_{||}$ and $f\sigma_8$ is improved by a factor of $1.11$ in our multi-tracer analysis, and in particular, the statistical uncertainty of $f\sigma_8$ is reduced by $11.6 \%$.