Rotating molecular outflows: the young T Tauri star in CB 26

Free access article

Issue		A&A Volume 494, Number 1, January IV 2009


Page(s)		147 - 156
Section		Interstellar and circumstellar matter
DOI		http://dx.doi.org/10.1051/0004-6361:200810835
Published online		11 December 2008

A&A 494, 147-156 (2009)
DOI: 10.1051/0004-6361:200810835

Rotating molecular outflows: the young T Tauri star in CB 26

R. Launhardt¹, Ya. Pavlyuchenkov^{1, 2}, F. Gueth³, X. Chen¹, A. Dutrey^{4, 5}, S. Guilloteau^{4, 5}, Th. Henning¹, V. Piétu³, K. Schreyer⁶, and D. Semenov¹

¹ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
e-mail: rl@mpia.de
² Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya 48, Moscow 109117, Russia
³ IRAM, 300 rue de la piscine, 38406 Saint-Martin-d'Hères, France
⁴ Université Bordeaux 1, Laboratoire d'Astrophysique de Bordeaux (LAB), France
⁵ CNRS/INSU – UMR5804, BP 89, 33270 Floirac, France
⁶ Astrophysikalisches Institut und Universitäts-Sternwarte, Schillergässchen 2-3, 07745 Jena, Germany

Received 20 August 2008 / Accepted 18 November 2008

Abstract
Context. The disk-outflow connection is thought to play a key role in extracting excess angular momentum from a forming proto-star. Although jet rotation has been observed in a few objects, no rotation of molecular outflows has been unambiguously reported so far.
Aims. We report new millimeter-interferometric observations of the edge-on T Tauri star – disk system in the isolated Bok globule CB 26. The aim of these observations was to study the disk-outflow relation in this 1 Myr old low-mass young stellar object.
Methods. The IRAM PdBI array was used to observe ¹²CO(2–1) at 1.3 mm in two configurations, resulting in spectral line maps with 1.5´´ resolution. We use an empirical parameterized steady-state outflow model combined with 2-D line radiative transfer calculations and $\chi^2$ -minimization in parameter space to derive a best-fit model and constrain parameters of the outflow.
Results. The data reveal a previously undiscovered collimated bipolar molecular outflow of total length $\approx$ 2000 AU, escaping perpendicular to the plane of the disk. We find peculiar kinematic signatures that suggest that the outflow is rotating with the same orientation as the disk. However, we could not ultimately exclude jet precession or two misaligned flows as possible origins of the observed peculiar velocity field. There is indirect indication that the embedded driving source is a binary system, which, together with the youth of the source, could provide a clue to the observed kinematic features of the outflow.
Conclusions. CB 26 is so far the most promising source in which to study the rotation of a molecular outflow. Assuming that the outflow is rotating, we compute and compare masses, mass flux, angular momenta, and angular momentum flux of the disk and outflow and derive disk dispersal timescales of $0.5 \ldots 1$ Myr, comparable to the age of the system.

Key words: circumstellar matter -- ISM: jets and outflows -- stars: pre-main sequence -- planetary systems: protoplanetary disks -- ISM: molecules

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