Superluminous quasars and mesolensing

TL;DR

This paper investigates whether gravitational mesolensing by intermediate-mass objects can significantly amplify the brightness of high-redshift quasars, potentially explaining their superluminous observed magnitudes.

Contribution

It provides an estimation of the fraction of quasars whose extreme luminosities could be due to gravitational mesolensing effects.

Findings

A significant fraction of superluminous quasars may be magnified by mesolensing.

Mesolensing could account for some quasars' apparent superluminosity without requiring extremely massive black holes.

The study offers a framework to distinguish between intrinsic luminosity and lensing amplification.

Abstract

Observed magnitudes of many quasars with redshifts exceeding $z=5$ correspond to luminosities $L_{\rm bol} > 10^{14}\,L_\odot$. The standard mechanism of quasar energy release by accretion suggests that masses of superluminous quasars should exceed $10^{10}\,M_\odot$. On the other hand, the age of these objects in the standard cosmological model is below one billion years, which is too short to explain their formation in the early Universe. Many quasars are known to be gravitationally lensed; showing multiple images of the same object. In the case of remote quasars with no multiple images, it is still possible that they are also gravitationally lensed by foreground objects of intermediate masses, such as globular clusters or dwarf galaxies. Such mesolensing would result in essential amplification of quasar brightnesses, subject to geometrical configuration between the lens and the lensed object. Here we estimate the fraction of quasars whose brightness might have been amplified by gravitational lensing.