Balmer Emission Line Profiles and the Complex Properties of Broad Line Regions in Active Galactic Nuclei

TL;DR

This study analyzes AGN spectra from SDSS using advanced line profile techniques to understand the complex structure of broad emission lines and improve estimates of AGN and host galaxy properties.

Contribution

It introduces a generalized line profile analysis method that accounts for the entire broad emission line profiles in AGN spectra.

Findings

Broad line profiles are complex and influenced by geometry and inclination.

Most BLRs have low inclination angles, typically less than 20 degrees.

Inclination effects decrease as line profiles become broader.

Abstract

In this work we analyze a sample of AGN spectra, selected from the 6th Data Release of the Sloan Digital Sky Survey, exploiting a generalized technique of line profile analysis, designed to take into account the whole profiles of their broad emission lines. We find that the line profile broadening functions result from a complex structure, but we may be able to infer some constraints about the role of the geometrical factor, thus improving our ability to estimate AGN properties and their relation with the host galaxy. Our results suggest that flattening and inclination within the structure of the Broad Line Region (BLR) must be taken into account. We detect low inclinations of the BLR motion plane with respect to our line of sight, typically i < 20 degrees, with a geometrical effect which generally decreases as the line profile becomes broader.