Searching for jet rotation in Class 0/I sources observed with GEMINI/GNIRS

¹ The Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland
e-mail: dac@cp.dias.ie
² INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
e-mail: fran@arcetri.astro.it
³ Centre for Astrophysics Research, University of Hertfordshire, Hatfield, HERTS AL10 9AB, UK
e-mail: a.chrysostomou@jach.hawaii.edu
⁴ INAF – Osservatorio Astronomico di Roma, via Frascati 33, 00044 Monteporzio Catone, Italy
e-mail: nisini@oa-roma.inaf.it
⁵ Joint Astronomy Centre, University Park, Hilo, Hawaii 96720, USA
e-mail: c.davis@jach.hawaii.edu

Received: 30 December 2009
Accepted: 24 November 2010

Abstract

Context. 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.

Aims. To test the validity of a rotation argument, we must extend the survey to a larger sample, including younger sources.

Methods. 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 of protostellar jets HH 34, HH 111-H, HH 212 NK1 and SK1.

Results. The [Fe II] emission was unresolved in all cases and so Doppler shifts across the jet width could not be accessed. The H₂ 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^-1 identified.

Conclusions. 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^-1 and 1  ×  10^-5   M_⊙ yr^-1 AU km s^-1 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.