Interpreting molecular hydrogen and atomic oxygen line emission of T Tauri disks with photoevaporative disk-wind models

TL;DR

This study uses hydrodynamic photoevaporative disk-wind models combined with thermo-chemical analysis to interpret molecular hydrogen and atomic oxygen emission lines in T Tauri disks, comparing results with observations to understand wind-driving mechanisms.

Contribution

It demonstrates that photoevaporative disk-wind models can explain observed spectral line signatures in T Tauri disks, highlighting the need for more detailed models to distinguish wind-driving processes.

Findings

Photoevaporative models match observed low-velocity blueshifted line components.

Simple spectral interpretation methods can be misleading.

Models cannot yet definitively identify wind-driving mechanisms.

Abstract

Winds in protoplanetary disks play an important role in their evolution and dispersal. However, what physical process is driving the winds is still unclear (i.e. magnetically vs thermally driven), and can only be understood by directly confronting theoretical models with observational data. We use hydrodynamic photoevaporative disk-wind models and post-process them with a thermo-chemical model to produce synthetic observables for the o-H$_2$ at 2.12 micron and [OI] at 0.63 micron spectral lines and directly compare the results to a sample of observations. Our photoevaporative disk-wind model is consistent with the observed signatures of the blueshifted narrow low-velocity component (NLVC), which is usually associated with slow disk winds, for both tracers. Only for one out of seven targets that show blueshifted NLVCs does the photoevaporative model fail to explain the observed line kinematics. Our results also indicate that interpreting spectral line profiles by simple methods, such as the thin-disk approximation, to determine the line emitting region can yield misleading conclusions. The photoevaporative disk-wind models are largely consistent with the studied observational data set, but it is not possible to clearly discriminate between different wind-driving mechanisms. Further improvements to the models, such as consistent modelling of the dynamics and chemistry and detailed modelling of individual targets would be beneficial. Furthermore, a direct comparison of magnetically driven disk-wind models to the observational data set is necessary in order to determine whether or not spatially unresolved observations of multiple wind tracers are sufficient to discriminate between theoretical models.