Standardizing reverberation-measured C iv time-lag quasars, and using them with standardized Mg ii quasars to constrain cosmological parameters.

We use 38 C  iv quasar (QSO) reverberation-mapped observations, which span eight orders of magnitude in luminosity and the redshift range 0.001064 ≤ z ≤ 3.368, to simultaneously constrain cosmological-model and QSO radius–luminosity (R–L) relation parameters in six cosmological models, using an improved technique that more correctly accounts for the asymmetric errors bars of the time-lag measurements. We find that R–L relation parameters are independent of the cosmological models used in the analysis and so the R–L relation can be used to standardize the C  iv QSOs. The C  iv QSO cosmological constraints are consistent with those from Mg  ii QSOs, allowing us to derive joint C  iv + Mg  ii QSO cosmological constraints which are consistent with currently accelerated cosmological expansion, as well as consistent with cosmological constraints derived using better-established baryon acoustic oscillation (BAO) and Hubble parameter [ H (z)] measurements. When jointly analysed with H (z) + BAO data, current C  iv + Mg  ii QSO data mildly tighten current H (z) + BAO data cosmological constraints. [ABSTRACT FROM AUTHOR]