FeII emission in NLS1s -- originating from denser regions with higher abundances?

TL;DR

This study models the broad-line region of quasars with a focus on FeII emission, exploring how geometry, density, and composition influence spectral features and their potential as cosmological tools.

Contribution

It introduces a model of the quasar broad-line region considering geometry, density, and composition effects on FeII emission, using the CLOUDY code to analyze spectral dependencies.

Findings

FeII emission depends on cloud density and composition.

Inclination angle influences spectral line parameters.

Modeling helps understand quasar spectral diversity.

Abstract

The interpretation of the main sequence of quasars has become a frontier subject in the last years. The consider the effect of a highly flattened, axially symmetric geometry for the broad-line region (BLR) on the parameters related to the distribution of quasars along their Main Sequence. We utilize the photoionization code CLOUDY to model the BLR, assuming `un-constant' virial factor with a strong dependence on the viewing angle. We show the preliminary results of the analysis to highlight the co-dependence of the Eigenvector 1 parameter, R$_{\mathrm{FeII}}$ on the broad H$\beta$ FWHM (i.e. the line dispersion) and the inclination angle ($\theta$), assuming fixed values for the Eddington ratio ($\mathrm{L_{bol}}/\mathrm{L_{Edd}}$), black hole mass ($\mathrm{M_{BH}}$) and spectral energy distribution (SED) shape. We consider four cases with changing cloud density (n$\rm{_{H}}$) and composition. Understanding the FeII emitting region is crucial as this knowledge can be extended to the use of quasars as distance indicators for Cosmology.