Redshift evolution and non-universal dispersion of quasar luminosity correlation

The standard ? cold dark matter (?CDM) model is recently reported to deviate from the high-redshift Hubble diagram of Type Ia supernovae (SNe) and quasars (QSOs) at similar to 4 sigma 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 ?CDM model and the marginalized 3 sigma 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 ?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 similar to 2.7 sigma and similar to 4 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 similar to 4 sigma deviation from the standard ?CDM probably originates from the redshift-evolution effects and non-universal dispersion of the QSO luminosity correlation rather than new physics.

Automated summary

This study combines the PAge approximation and a high-quality QSO sample to investigate the deviation of the standard CDM model from the high-redshift Hubble diagram of SNe and QSOs. The results suggest that this deviation may originate from the redshift-evolution effects and non-universal dispersion of the QSO luminosity correlation.