Confronting a Thin Disk-Wind Launching Mechanism of Broad-Line Emission in AGN with GRAVITY Observations of Quasar 3C 273

TL;DR

This study tests a thin disk-wind model for broad-line emission in quasar 3C 273 using GRAVITY interferometric data, finding it fits the data but is inconsistent with observed jet orientation, challenging its validity.

Contribution

It introduces and evaluates a disk-wind model for broad-line emission in quasars, contrasting it with cloud-based models using high-resolution interferometric data.

Findings

The disk-wind model can fit the interferometric data statistically.

The model requires a high inclination angle not supported by jet observations.

Cloud models remain more consistent with observed jet orientations.

Abstract

Quasars show a remarkable degree of atomic emission line-broadening, an observational feature which, in conjunction with a radial distance estimate for this emission from the nucleus is often used to infer the mass of the central supermassive black hole. The radius estimate depends on the structure and kinematics of this so-called Broad-Line Region (BLR), which is often modeled as a set of discrete emitting clouds. Here, we test an alternative kinematic disk-wind model of optically thick line emission originating from a geometrically thin accretion disk under Keplerian rotation around a supermassive black hole. We use this model to calculate broad emission line profiles and interferometric phases to compare to GRAVITY data and previously published cloud modelling results. While we show that such a model can provide a statistically satisfactory fit to GRAVITY data for quasar 3C 273, we disfavor it as it requires 3C 273 be observed at high inclination, which observations of the radio jet orientation do not support.