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We use observations of 66 reverberation-measured \Mgii\ quasars (QSOs) in theredshift range $0.36 \leq z \leq 1.686$ -- a subset of the 78 QSOs wepreviously studied that also have \rfe\ (flux ratio parameter of UV \Feii\ to\Mgii\ that is used as an accretion-rate proxy) measurements -- tosimultaneously constrain cosmological model parameters and QSO 2-parameter and3-parameter radius-luminosity ($R-L$) relation parameters in six differentcosmological models. We find that these QSO $R-L$ relation parameters areindependent of the assumed cosmological model and so these QSOs arestandardizable through the $R-L$ relations. Also: (1) With the 2-parameter$R-L$ relation, we find that the low-\rfe\ and high-\rfe\ data subsets obey thesame $R-L$ relation within the error bars. (2) Extending the 2-parameter $R-L$relation to a 3-parameter one does not result in the hoped-for reduction in theintrinsic dispersion of the $R-L$ relation. (3) Neither of the 3-parameter$R-L$ relations provide a significantly better fit to the measurements thandoes the 2-parameter $R-L$ relation. These are promising results for theon-going development of \Mgii\ cosmological probes. The first and third ofthese results differ significantly from those we found elsewhere from analysesof reverberation-measured \hb\ QSOs.

monthly notices of the royal astronomical society

Consistency study of high- and low-accreting Mg ii quasars: No  significant effect of the Fe ii to Mg ii flux ratio on the radius-luminosity  relation dispersion