Optical and UV properties of a radio-loud and a radio-quiet Population A quasar at high redshift

TL;DR

This study compares the optical and UV spectral properties of a high-redshift radio-loud and a radio-quiet Population A quasar, revealing similarities in optical features but notable differences in UV emission line behaviors.

Contribution

It provides a detailed spectroscopic analysis highlighting how radio-loudness influences UV emission line properties in high-redshift Population A quasars.

Findings

Both quasars share similar optical spectral properties.

Significant UV line blueshifts observed in both sources.

Distinct UV spectral behaviors between radio-loud and radio-quiet quasars.

Abstract

Different properties of quasars may be observed and analysed through the many ranges of the electromagnetic spectrum. Pioneering studies showed that an "H-R diagram" for quasars was needed to organize these data, and that more than two dimensions were necessary: a four dimensional Eigenvector (4DE1) parameter space was proposed. The 4DE1 makes use of independent observational properties obtained from the optical and UV emission lines, as well as from the soft-X rays. The 4DE1 "optical plane", also known as the quasar Main Sequence (MS), identifies different spectral types in order to describe a consistent picture of QSOs. In this work we present a spectroscopic analysis focused on the comparison between two sources, one radio-loud (PKS2000-330, z = 3.7899) and one radio-quiet (Q1410+096, z = 3.3240), both showing Population A quasar spectral properties. Optical spectra were observed in the infrared with VLT/ESO, and the additional measures in UV were obtained through the fitting of archive spectra. The analysis was performed through a non-linear multi-component decomposition of the emission line profiles. Results are shown in order to highlight the effects of the radio-loudness on their emission line properties. The two quasars share similar optical spectroscopic properties and are very close on the MS classification while presenting significant differences on the UV data. Both sources show significant blueshifts in the UV lines but important differences in their UV general behaviour. While the radio-quiet source Q1410+096 shows a typical Pop A UV spectrum with similar intensities and shapes on both CIV1549 and SiIV1392, the UV spectrum of the strong radio-loud PKS2000-330 closely resembles the one of population B of quasars.