Isolating an outflow component in single-epoch spectra of quasars

TL;DR

This paper investigates methods to isolate outflow components in single-epoch quasar spectra, addressing the challenge of distinguishing outflow signatures from other kinematic features in broad emission lines.

Contribution

It introduces an analysis approach for identifying outflow signatures in the Hβ line profiles of quasars, improving the understanding of quasar outflows in single-epoch spectra.

Findings

Outflow features are detected across a wide luminosity range.

Profile shapes indicative of outflows are identified in both composite and individual spectra.

Analysis aids in better dynamical modeling of quasar emission regions.

Abstract

Gaseous outflows appear to be a universal property of type-1 and type-2 active galactic nuclei (AGN). The main diagnostic is provided by emission features shifted to higher frequency via the Doppler effect, implying that the emitting gas is moving toward the observer. However, beyond the presence of blueshift, the observational signatures of the outflows are often unclear, and no established criteria exist to isolate the outflow contribution in the integrated, single-epoch spectra of type-1 AGN. The emission spectrum collected with the typical apertures of long-slit spectroscopy or of fiber optics sample contributions over a broad range of spatial scales, making it difficult to analyze the line profiles in terms of different kinematic components. Nevertheless, hundred of thousands of quasars spectra collected at moderate resolution demand a proper analysis of the line profiles for proper dynamical modelling of the emitting regions. In this small contribution we shall analyze several profiles of the HI Balmer line H\b{eta} from composite and individual optical spectra of sources radiating at moderate Eddington ratio (Population B following Sulentic et al. 2000). Features and profile shapes that might be traced to outflow due to narrow-line region gas are detected over a wide range of luminosity.