A Semi-Analytical Line Transfer (SALT) Model II: the effects of a Bi-Conical geometry

TL;DR

This paper extends the SALT model to bi-conical galactic outflows, analyzing how geometry influences spectral line profiles and demonstrating reliable recovery of geometric parameters from simulated data.

Contribution

It introduces a generalized SALT model for bi-conical geometries and assesses the recoverability of outflow parameters from spectral profiles.

Findings

Geometrical parameters are accurately recovered.

Density and velocity fields are reliably determined when both absorption and emission are visible.

Certain geometries, like narrow cones perpendicular to the line of sight, remain unconstrained.

Abstract

We generalize the semi-analytical line transfer (SALT) model recently introduced by Scarlata \& Panagia (2015) for modeling galactic outflows, to account for bi-conical geometries of various opening angles and orientations with respect to the line-of-sight to the observer, as well as generalized velocity fields. We model the absorption and emission component of the line profile resulting from resonant absorption in the bi-conical outflow. We show how the outflow geometry impacts the resulting line profile. We use simulated spectra with different geometries and velocity fields to study how well the outflow parameters can be recovered. We find that geometrical parameters (including the opening angle and the orientation) are always well recovered. The density and velocity field parameters are reliably recovered when both an absorption and an emission component are visible in the spectra. This condition implies that the velocity and density fields for narrow cones oriented perpendicular to the line of sight will remain unconstrained.