Redshift evolution and non-universal dispersion of quasar luminosity correlation

Abstract

ABSTRACT The standard Λ cold dark matter (ΛCDM) model is recently reported to deviate from the high-redshift Hubble diagram of Type Ia supernovae (SNe) and quasars (QSOs) at ∼4σ confidence level. In this work, we combine the PAge approximation (a nearly model-independent parametrization) and a high-quality QSO sample to search for the origins of the deviation. By visualizing the ΛCDM model and the marginalized 3σ constraints of SNe+QSOs into the PAge space, we confirm that the SNe+QSO constraints in both flat and non-flat PAge cases are in remarkable tension with the standard ΛCDM cosmology. Next, we investigate the tension from the perspective of redshift-evolution effects. We find that the QSO correlation coefficient γ calibrated by SNe+low-z QSOs and SNe+high-z QSOs shows ∼2.7σ and ∼4σ tensions in flat and non-flat universes, respectively. The tensions for intrinsic dispersion δ between different data sets are found to be >4σ 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 ∼4σ deviation from the standard ΛCDM probably originates from the redshift-evolution effects and non-universal dispersion of the QSO luminosity correlation rather than new physics.