Highly Accreting Quasars: Sample Definition and Possible Cosmological Implications

TL;DR

This paper introduces a new method to identify highly accreting quasars near the Eddington limit across various spectral ranges, enabling redshift-independent luminosity estimates and potential cosmological constraints.

Contribution

It presents a novel selection technique for extreme Eddington ratio quasars and demonstrates their use in testing cosmological models with preliminary data.

Findings

Method can identify quasars near the Eddington limit across spectral ranges.

Preliminary results align with concordance cosmology.

Mock data suggest potential for tight cosmological constraints.

Abstract

We propose a method to identify quasars radiating closest to the Eddington limit, defining primary and secondary selection criteria in the optical, UV and X-ray spectral range based on the 4D eigenvector 1 formalism. We then show that it is possible to derive a redshift-independent estimate of luminosity for extreme Eddington ratio sources. Using preliminary samples of these sources in three redshift intervals (as well as two mock samples), we test a range of cosmological models. Results are consistent with concordance cosmology but the data are insufficient for deriving strong constraints. Mock samples indicate that application of the method proposed in this paper using dedicated observations would allow to set stringent limits on Omega_M and significant constraints on Omega_Lambda.