Hydrogen Balmer Emission Lines and the Complex Broad Line Region Structure

TL;DR

This study analyzes the broad Balmer emission lines in Type 1 AGN to understand the structure of the broad line region, revealing flattened geometries at low inclinations and their relation to the central engine's properties.

Contribution

It introduces a combined line profile and kinematical modeling approach to probe the structure of the broad line region in AGN, highlighting flattened geometries at low inclinations.

Findings

Broad emission lines are consistent with flattened structures at inclinations below 20 degrees.

A relationship between kinematical and thermo-dynamical properties of AGN is identified.

The results align with independent radio observations, supporting the proposed geometrical model.

Abstract

In this work we investigate the properties of the broad emission line components in the Balmer series of a sample of Type 1 Active Galactic Nuclei (AGN). Using the Boltzmann Plot method as a diagnostic tool for physical conditions in the plasma, we detect a relationship among the kinematical and thermo-dynamical properties of these objects. In order to further clarify the influence of the central engines on the surrounding material, we look for signatures of structure in the broad line emitting regions, that could affect the optical domain of the observed spectra. Using a combination of line profile analysis and kinematical modeling of the emitting plasma, we study how the emission line broadening functions are influenced by different structural configurations. The observed profiles are consistent with flattened structures seen at quite low inclinations, typically smaller than 20 degrees. Since this result is in good agreement with some independent observations at radio frequencies, we apply a new formalism to study the properties of AGN central engines.