Quasar standardization: Overcoming Selection Biases and Redshift Evolution

Understand

Quasars (QSOs) are extremely luminous active galatic nuclei currently observed up to redshift $z=7.642$.

• As such, they have the potential to be the next rung of the cosmic distance ladder beyond SNe Ia, if they can reliably be used as cosmological probes.
• The main issue in adopting QSOs as standard candles (similarly to Gamma-Ray Bursts) is the large intrinsic scatter in the relations between their observed properties.
• This could be overcome by finding correlations among their observables that are intrinsic to the physics of QSOs and not artifacts of selection biases and/or redshift evolution.