Variability in Quasar Light Curves: using quasars as standard candles

TL;DR

This study identifies a correlation between quasar light curve variability and their mean absolute magnitude, suggesting quasars could serve as reliable, model-independent standard candles for measuring cosmic distances at high redshifts.

Contribution

It establishes a new relation between variability slope and luminosity in quasars, enhancing their potential as standard candles for cosmology.

Findings

Relation between variability slope and mean magnitude with 0.15 dex dispersion.

Potential to measure luminosity distances independently of cosmological models.

Extension of the cosmic distance ladder beyond supernova redshifts.

Abstract

A relation between the variational slope, $s_F$ , and the mean absolute magnitude, $\langle M \rangle$, in the light curves of 58 spectroscopically confirmed quasars is measured with a dispersion of 0.15dex. Assuming it holds for quasars in general, not only does this relation add to our working knowledge of quasar variability but it also shows great promise at accurately measuring luminosity distance to a quasar in a model independent way. An accurate, model independent measure of the luminosity distance would allow quasars to be added to the cosmic distance ladder, easily extending the ladder out far beyond the redshifts accessible to type Ia supernovae where cosmological parameters can be better constrained.