Probing Protoplanetary Disk Winds with C II Absorption

TL;DR

This study analyzes C II absorption in 40 T Tauri stars to characterize disk wind velocities and origins, revealing that both fast and slow winds are consistent with thermal-magnetized models and originate mainly from the inner disk.

Contribution

It introduces semi-analytical models for disk wind absorption and provides observational evidence linking wind features to disk inclination and ionization states.

Findings

Fast wind velocity decreases with disk inclination.

Slow wind absorption occurs mainly in higher inclination disks.

Both wind types align with thermal-magnetized disk wind models.

Abstract

We present an analysis of wind absorption in the C II ${\lambda}1335$ doublet towards 40 classical T Tauri stars with archival far-ultraviolet (FUV) spectra obtained by the Hubble Space Telescope. Absorption features produced by fast or slow winds are commonly detected (36 out of 40 targets) in our sample. The wind velocity of the fast wind decreases with disk inclination, consistent with expectations for a collimated jet. Slow wind absorption is detected mostly in disks with intermediate or high inclination, without a significant dependence of wind velocity on disk inclination. Both the fast and slow wind absorption are preferentially detected in FUV lines of neutral or singly ionized atoms. The Mg II ${\lambda}{\lambda}2796,2804$ lines show wind absorption consistent with the absorption in the C II lines. We develop simplified semi-analytical disk/wind models to interpret the observational disk wind absorption. Both fast and slow winds are consistent with expectations from a thermal-magnetized disk wind model and are generally inconsistent with a purely thermal wind. Both the models and the observational analysis indicate that wind absorption occurs preferentially from the inner disk, offering a wind diagnostic in complement to optical forbidden line emission that traces the wind in larger volumes.