2022MNRAS.516.1721C

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.