The distance scale and Eddington efficiency of luminous quasars

TL;DR

This paper explores how luminous quasars can be used to measure the Hubble constant independently of traditional distance ladders, by analyzing the relation between black hole mass, luminosity, and cosmological parameters.

Contribution

It introduces a method to estimate the Hubble constant using quasar properties, leveraging the calibration of black hole mass without dependence on H_0, and discusses its potential for cosmology.

Findings

H_0 can be constrained using luminous quasars radiating near the Eddington limit.

The method is robust against changes in mbda_{ m mbda} in flat cosmological models.

Preliminary analysis suggests H_0 > 45 km/s/Mpc from luminous quasar data.

Abstract

The relation between the central mass and quasar luminosity (M_BH \propto L^{\alpha}FHWM^2) links a given Eddington ratio with a value of H_0, within a cosmology with fixed (\Omega_m,\Omega_{\Lambda}). We point out that because the relation is calibrated at low z using distance independent reverberation mapping to get the BLR size, the derived M_BH interestingly does not depend on H_0, while L/L_Edd is sensitive to H_0, but rather robust to changes of \Omega_{\Lambda} in the standard flat model. This means, e.g., that enough of extragalactic objects radiating at the Eddington limit could be used to study the global Hubble constant in a new way, bypassing the local distance ladder. The method could become practical when systematic errors in derived M_BH are understood and objects with L /leq L_Edd can be independently identified. As an illustration, if we take a sample of tranquil very luminous quasars in the redshift range 0.5 < z < 1.6, and assume that they are radiating with L_bol \leq L_Edd, then the usual numeric factors used for calculating M_BH and L_bol would lead to the result that the Hubble constant must be larger than 45 km/s/Mpc.