Kinematics from spectral lines for AGN outflows based on time-independent radiation-driven wind theory

TL;DR

This paper develops a velocity-dependent photoionization model for AGN outflows, successfully reproducing observed spectral features and revealing the necessity of two distinct outflow components with different ionization states.

Contribution

It introduces a novel, detailed model of AGN outflows based on radiation-driven wind theory that matches observed spectral line profiles and asymmetries.

Findings

The model reproduces the ionization-velocity relationship in NGC 3783.

Two outflow components are needed to explain line asymmetries.

The model links X-ray and UV absorption features through shared outflow components.

Abstract

We build a bulk velocity-dependent photoionization model of the warm absorber of the Seyfert 1 galaxy NGC 3783. By adopting functional forms for velocity of the flow and its particle density with radius, appropriate for radiation driven winds, we compute the ionization, temperature, line Doppler shift, and line optical depths as a function of distance. By doing this we obtain detailed profiles for the entire absorption line spectrum. The model reproduces the observed relationship between the gas ionization and the velocity shift of the line centroids as well as the asymmetry of the absorption lines in the X-ray spectrum of NGC 3783. It is found that the distribution of asymmetry requires the presence of two outflows: a higher ionization component responsible for the blue wings of the high ionization lines and the red wings of the low ionization oxygen lines, and a lower ionization flow that makes up for the blue wings of the oxygen lines. Our model predicts a relationship between the X-rays and the UV absorbers, where the component creating the long wavelength lines in the X-ray spectrum is also responsible for creating at least part of the UV absorption troughs.