A New Orientation Indicator for Radio-Quiet Quasars

TL;DR

This paper introduces a new orientation indicator for radio-quiet quasars based on emission line velocities, enabling separation of orientation and accretion effects on observed properties.

Contribution

It presents a novel method to distinguish orientation and Eddington ratio effects in quasars using emission line velocity offsets and morphology data.

Findings

Orientation affects emission line velocities and observed luminosity.

Eddington ratio influences broad line region properties.

Orientation and Eddington ratio effects are quantifiable in quasar spectra.

Abstract

The velocities of the [O III] 5007 and optical Fe II emission lines, measured relative to the systemic redshifts of 2265 QSOs by Hu et al. (2008), show the signature of a disklike BLR structure with polar outflows. Objects with large [O III] outflows show no Fe II offset velocity and are seen pole-on. Objects with large Fe II inflow show no [O III] offset velocity and are seen edge-on. This interpretation is supported by the morphology of the radio-loud objects within the sample and by previous determinations of the geometry of the broad and narrow line regions. Analysis of the objects with neither Fe II or [O III] velocity offsets, however, show that the two groups also differ in Eddington ratio, and, within this subset, corresponding groups with high and low Eddington ratio but with the opposite orientation can be identified. Using these four subsets of the sample, the effects of orientation and Eddington ratio can be separated, and, in some cases, quantified. The changes in apparent continuum luminosity and broad H-beta width and strength suggest a model in which both continuum and H-beta are emitted from the surface of the disk, which is less flattened in high Eddington ratio objects. The effects of orientation on the derived properties, black hole mass and Eddington ratio, are significant, though not large. The [O III] outflow appears to influence the width of that line, as well as its centroid.