Searching for Jet Rotation in Class 0/I Sources observed with GEMINI/GNIRS

TL;DR

This study investigates potential jet rotation in young stellar objects by analyzing radial velocity gradients in Class 0/I jets using high-resolution infrared spectroscopy, highlighting the challenges and complexities in confirming jet rotation observationally.

Contribution

The paper presents new radial velocity measurements of molecular jets from Class 0/I sources, emphasizing the difficulties in detecting jet rotation and the need for higher resolution observations.

Findings

Detected velocity gradients suggestive of jet rotation.

Observed asymmetries imply complex jet kinematics.

External influences may affect velocity measurements.

Abstract

In recent years, there has been a number of detections of gradients in the radial velocity profile across jets from young stars. The significance of these results is considerable. They may be interpreted as a signature of jet rotation about its symmetry axis, thereby representing the only existing observational indications supporting the theory that jets extract angular momentum from star-disk systems. However, the possibility that we are indeed observing jet rotation in pre-main sequence systems is undergoing active debate. To test the validity of a rotation argument, we must extend the survey to a larger sample, including younger sources. We present the latest results of a radial velocity analysis on jets from Class 0 and I sources, using high resolution data from the infrared spectrograph GNIRS on GEMINI South. We obtained infrared spectra protostellar jets HH 34, HH 111-H, HH 212 NK1 and SK1. The [Fe II] emission was unresolved in all cases and so Doppler shifts across the jet width could not be accessed. The H_2 emission was resolved in all cases except HH 34. Doppler profiles across the molecular emission were obtained, and gradients in radial velocity of typically 3 km/s identified. Agreement with previous studies implies they may be interpreted as jet rotation, leading to toroidal velocity and angular momentum flux estimates of 1.5 km/s and 1x10^-5 M_odot/yr AU km/s respectively. However, caution is needed. For example, emission is asymmetric across the jets from HH 212 suggesting a more complex interpretation is warranted. Furthermore, observations for HH 212 and HH 111-H are conducted far from the source implying external influences are more likely to confuse the intrinsic flow kinematics. These observations demonstrate the difficulty of conducting this study from the ground, and highlight the necessity for high angular resolution via adaptive optics or space-based facilities.