Using quasar X-ray and UV flux measurements to constrain cosmological model parameters

Understand

Risaliti and Lusso have compiled X-ray and UV flux measurements of 1598 quasars (QSOs) in the redshift range $0.036 \leq z \leq 5.1003$, part of which, $z \sim 2.4 - 5.1$, is largely cosmologically unprobed.

• In this paper we use these QSO measurements, alone and in conjunction with baryon acoustic oscillation (BAO) and Hubble parameter [$H(z)$] measurements, to constrain cosmological parameters in six different cosmological models, each with two different Hubble constant priors.
• In most of these models, given the larger uncertainties, the QSO cosmological parameter constraints are mostly consistent with those from the $H(z)$ + BAO data.
• A somewhat significant exception is the non-relativistic matter density parameter $\Omega_{m0}$ where the QSO data favors $\Omega_{m0} \sim 0.5 - 0.6$ in most models.