Line Profile studies of Hydrodynamical Models of Cometary Compact H II Regions

TL;DR

This study compares line profile signatures of hydrodynamical models of cometary H II regions, revealing how different models and stellar velocities influence observable spectral lines, aiding in distinguishing physical mechanisms.

Contribution

It introduces detailed line profile calculations for champagne flow and bow shock models, providing diagnostic tools to differentiate these models based on spectral line observations.

Findings

Bow shock profiles differ from champagne flow profiles, especially at low stellar velocities.

Velocity directions of emission lines depend on stellar speed and model type.

Line profiles along the symmetry axis help distinguish between models.

Abstract

We simulate evolution of cometary H II regions based on several champagne flow models and bow shock models, and calculate the profiles of the [Ne II] fine-structure line at $12.81\mu m$, the $H30\alpha$ recombination line and the [Ne III] fine-structure line at $15.55\mu m$ for these models at different inclinations of $0^o, 30^o \textrm{and} 60^o$. We find that the profiles in the bow shock models are generally different from those in the champagne flow models, but the profiles in the bow shock with lower stellar velocity ($\leq5km s^{-1}$) are similar to those in the champagne flow models. In champagne flow models, both the velocity of peak flux and the flux weighted central velocities of all three lines are pointing outward from molecular clouds. In bow shock models, the directions of these velocities rely on the speed of stars. They have the similar motion in high stellar speed case but opposite directions in low stellar speed case. We notice that the line profiles from the slit along the symmetrical axis of the projected 2D image of these models are useful for distinguishing bow shock models and champagne flow models. It is also confirmed by the calculation that the flux weighted central velocity and the line luminosity of the [Ne III] line can be estimated from the [Ne II] line and the $H30\alpha$ line.