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Astron. Astrophys. 327, 671-680 (1997)

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Sub-arcsecond morphology and kinematics of the DG Tauri jet in the [O I ] [FORMULA] 6300 line *

Claudia Lavalley 1, Sylvie Cabrit 2, Catherine Dougados 1, Pierre Ferruit 3 and Roland Bacon 3

1 Laboratoire d'Astrophysique, Observatoire de Grenoble, UMR CNRS 5571, Université Joseph Fourier, B.P.53X, F-38041, Grenoble Cedex 9, France
2 Observatoire de Paris, DEMIRM, URA 336 du CNRS, 61 Avenue de l'Observatoire, F-75014 Paris, France
3 Observatoire de Lyon, UMR CNRS 5574, 9, av. Charles André, F-69561 Saint-Genis-Laval Cedex, France

Received 27 June 1996 / Accepted 5 May 1997

Abstract

We present the first 3D spectro-imaging observations of the [O I ] [FORMULA] 6300 line in an active T Tauri star: DG Tau. The morphological structure of the mass outflow is revealed with unprecedented spatial resolution (0.35 [FORMULA]). It consists of an unresolved inner peak containing two thirds of the total line flux, followed by a collimated jet-like body extending out to [FORMULA] from the star, and two resolved knots at distances of [FORMULA] and 4 [FORMULA]. One of the outer knots possesses a curved morphology and transverse velocity gradient strongly suggestive of a resolved bowshock. Time variability in the ejection velocity (with timescale [FORMULA] t [FORMULA] 8.5 yr) could explain the presence of such a bowshock, the spacing of knots at distances [FORMULA] from the star, and the strong velocity gradients along the jet observed closer to the star. The unresolved inner peak, centered at [FORMULA] 20 AU of the star, is apparently stationary and possibly linked to the initial jet collimation. Our size limit and absolute photometry for this peak set new constraints on the jet mass loss rate (between [FORMULA] and [FORMULA] yr-1), lowering previous estimates by a factor 5 to 25. Finally, our high sensitivity combined with velocity information allows us to detect unambiguously the counterjet of the system (v [FORMULA] +230 km/s), and to establish the existence of a diffuse halo of low-velocity [O I ] emission, which might trace a wider flow or an extended scattering nebula.

Key words: stars: pre-main sequence – stars: mass-loss – ISM: jets and outflows – stars: individual: DG Tau

* Based on observations collected at the Canada-France-Hawaii Telescope, operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique, and University of Hawaii.

Send offprint requests to: Claudia Lavalley

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© European Southern Observatory (ESO) 1997

Online publication: April 6, 1998
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