Redshift Evolution and Non-Universal Dispersion of Quasar Luminosity Correlation

TL;DR

This study investigates the deviation of quasar and supernova data from the standard cosmological model, attributing the discrepancy to redshift evolution and non-universal dispersion in quasar luminosity correlations rather than new physics.

Contribution

It demonstrates that redshift-dependent effects and intrinsic dispersion in quasar luminosity correlations explain the observed deviations from the $ ext{Lambda}$CDM model.

Findings

Significant tension between SNe+QSOs constraints and $ ext{Lambda}$CDM in PAge space.

Detected $ ext{2.7}\sigma$ and $ ext{4}\sigma$ tensions in correlation coefficient $oldsymbol{\gamma}$.

Intrinsic dispersion $oldsymbol{\delta}$ shows $>4 \sigma$ differences across data sets.

Abstract

The standard $\Lambda$CDM model is recently reported to deviate from the high-redshift Hubble diagram of type Ia supernovae (SNe) and quasars (QSOs) at $\sim4\sigma$ confidence level. In this work, we combine the PAge approximation (a nearly model-independent parameterization) and a high-quality QSO sample to search for the origins of the deviation. By visualizing the $\Lambda$CDM model and the marginalized $3\sigma$ constraints of SNe+QSOs into PAge space, we confirm that the SNe+QSOs constraints in both flat and non-flat PAge cases are in remarkable tension with the standard $\Lambda$CDM cosmology. Next, we investigate the tension from the perspective of redshift-evolution effects. We find that the QSO correlation coefficient $\gamma$ calibrated by SNe+low-z QSOs and SNe+high-z QSOs shows $\sim2.7\sigma$ and $\sim4\sigma$ tensions in flat and non-flat universes, respectively. The tensions for intrinsic dispersion $\delta$ between different data sets are found to be $>4\sigma$ in both flat and non-flat cases. These results indicate that the QSO luminosity correlation suffers from significant redshift evolution and non-universal intrinsic dispersion. Using a redshift-dependence correlation to build QSO Hubble diagram could lead to biases. Thus, the $\sim4\sigma$ deviation from the standard $\Lambda$CDM probably originates from the redshift-evolution effects and non-universal dispersion of the QSO luminosity correlation rather than new physics.