The Near-Infrared Broad Emission Line Region of Active Galactic Nuclei -- I. The Observations

TL;DR

This study provides high-quality near-infrared and optical spectra of 23 active galactic nuclei, analyzing their broad emission lines to understand the physics of their broad-line regions, including excitation mechanisms and iron emission.

Contribution

First simultaneous near-IR and optical spectroscopic observations of AGN broad emission lines, with detailed analysis of line identifications, excitation mechanisms, and iron emission spectrum.

Findings

Dominance of hydrogen, helium, oxygen, calcium, and iron lines in near-IR spectra

First confrontation of theoretical iron emission predictions with observations

Insights into excitation mechanisms of neutral oxygen in AGN

Abstract

We present high quality (high signal-to-noise ratio and moderate spectral resolution) near-infrared (near-IR) spectroscopic observations of 23 well-known broad-emission line active galactic nuclei (AGN). Additionally, we obtained simultaneous (within two months) optical spectroscopy of similar quality. The near-IR broad emission line spectrum of AGN is dominated by permitted transitions of hydrogen, helium, oxygen, and calcium, and by the rich spectrum of singly-ionized iron. In this paper we present the spectra, line identifications and measurements, and address briefly some of the important issues regarding the physics of AGN broad emission line regions. In particular, we investigate the excitation mechanism of neutral oxygen and confront for the first time theoretical predictions of the near-IR iron emission spectrum with observations.