Hbeta Profiles in Quasars: Evidence for an Intermediate-line Region

TL;DR

This study analyzes Hbeta and Fe II emission lines in quasars, revealing an intermediate-line region with distinct kinematics, suggesting a layered structure within the broad-line region.

Contribution

It provides evidence for an intermediate-line region in quasars, characterized by unique kinematic properties and spatial location, expanding understanding of quasar emission line regions.

Findings

Identification of an intermediate-width Hbeta component

Lack of correlation between intermediate and very broad components

Intermediate-line region likely dominated by infall dynamics

Abstract

We report on a systematic investigation of the Hbeta and Fe II emission lines in a sample of 568 quasars within z < 0.8 selected from the Sloan Digital Sky Survey. The conventional broad Hbeta emission line can be decomposed into two components--one with intermediate velocity width and another with very broad width. The velocity shift and equivalent width of the intermediate-width component do not correlate with those of the very broad component of Hbeta, but its velocity shift and width do resemble Fe II. Moreover, the width of the very broad component is roughly 2.5 times that of the intermediate-width component. These characteristics strongly suggest the existence of an intermediate-line region, whose kinematics seem to be dominated by infall, located at the outer portion of the broad-line region.