Optical and near-UV spectroscopic properties of low-redshift jetted quasars in the main sequence context.

This paper presents new optical and near-UV spectra of 11 extremely powerful jetted quasars, with radio to optical flux density ratio >103, which concomitantly cover the low-ionization emission of Mg  ii λ2800 and h β as well as the Fe  ii blends in the redshift range 0.35 ≲ z ≲ 1. We aim to quantify broad emission line differences between radio-loud (RL) and radio-quiet (RQ) quasars by using the 4D eigenvector 1 parameter space and its main sequence (MS) and to check the effect of powerful radio ejection on the low-ionization broad emission lines. The h β and Mg  ii λ2800 emission lines were measured by using non-linear multicomponent fittings as well as by analysing their full profile. We found that broad emission lines show large redward asymmetry both in h β and Mg  ii λ2800. The location of our RL sources in a UV plane looks similar to the optical one, with weak Fe  ii UV emission and broad Mg  ii λ2800. We supplement the 11 sources with large samples from previous work to gain some general inferences. We found that, compared to RQ, our extreme RL quasars show larger median h β full width at half maximum (FWHM), weaker Fe  ii emission, larger M BH, lower L bol/ L Edd, and a restricted bf space occupation in the optical and UV MS planes. The differences are more elusive when the comparison is carried out by restricting the RQ population to the region of the MS occupied by RL sources, albeit an unbiased comparison matching M BH and L bol/ L Edd suggests that the most powerful RL quasars show the highest redward asymmetries in h β. [ABSTRACT FROM AUTHOR]