Effects of heterogeneous data sets and time-lag measurement techniques on cosmological parameter constraints from MgII and CIV reverberation-mapped quasar data

Shulei Cao, Michal Zajaček, Bożena Czerny, Swayamtrupta Panda, Bharat Ratra

Published 2023-09-28Version 1

Previously, we demonstrated that MgII and CIV reverberation-mapped quasars (RM QSOs) are standardizable and that the cosmological parameters inferred using the broad-line region radius-luminosity (R-L) relation are consistent with those determined from better-established cosmological probes. With more data expected from ongoing and future spectroscopic and photometric surveys, it is imperative to examine how new QSO data sets of varied quality, with their own specific luminosity and time-delay distributions, can be best used to determine more restrictive cosmological parameter constraints. In this study, we test the effect of adding 25 OzDES MgII RM QSOs as well as 25 lower-quality SDSS RM CIV QSOs to our previous sample of RM QSOs. Although cosmological parameter constraints become tighter after adding these new QSOs, the new combined data sets have an increased maximum difference in R-L relation parameter values (with a > 2sigma difference in some R-L relation intercepts between cosmological models), and thus a lower standardizability for the larger MgII + CIV compilation. Different time-delay methodologies, particularly the ICCF and CREAM methods used for inferring time delays of SDSS RM QSOs, slightly affect cosmological and R-L relation parameter values, however, the effect is negligible for (smaller) compilations of robust time-delay detections.