EDP Sciences
Free access
Volume 416, Number 1, March II 2004
Page(s) 213 - 219
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20034531

A&A 416, 213-219 (2004)
DOI: 10.1051/0004-6361:20034531

Detection of a warm molecular wind in DG Tauri

M. Takami1, A. Chrysostomou1, T. P. Ray2, C. Davis3, W. R. F. Dent4, J. Bailey5, M. Tamura6 and H. Terada7

1  Department of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield, Herts AL10 9AB, UK
2  School of Cosmic Physics, Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin 2, Ireland
3  Joint Astronomy Centre, 660 North A'ohoku Place, University Park, Hilo, Hawaii 96720, USA
4  UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
5  Anglo-Australian Observatory, PO Box 296, Epping, NSW 1710, Australia
6  National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588, Japan
7  Subaru Telescope, 650 North A'ohoku Place, Hilo, Hawaii 96720, USA

(Received 17 October 2003 / Accepted 24 November 2003 )

We detect near-infrared H 2 emission in DG Tau using the Infrared Camera and Spectrograph (IRCS) on the 8.2-m SUBARU telescope. The spectra obtained along the jet axis show that the centroidal position of the 1-0 S(1) emission is offset by 0.2 '' from the star towards the jet, while those obtained perpendicular to the jet axis show a marginal extension, indicating that the emission line region has a typical width of ~0.6 ''. Their line profiles show a peak velocity of ~15 km s -1 blueshifted from the systemic velocity. These results indicate that the emission originates from a warm molecular wind with a flow length and width of ~40 and ~80 AU, respectively. The line flux ratios ( $I_{1-0 {\rm S}(0)}/I_{1-0 {\rm S}(1)}$ and an upper limit for $I_{2-1 {\rm S}(1)}/I_{1-0 {\rm S}(1)}$) suggest that the flow is thermalized at a temperature of ~2000 K, and is likely heated by shocks or ambipolar diffusion. The observed velocity and spatial extension suggest that the H 2 and forbidden line emission originate from different components of the same flow, i.e., a fast and partially ionised component near the axis and a slow molecular component surrounding it. Such a flow geometry agrees with model predictions of magneto-centrifugal driven winds.

Key words: line: formation -- stars: pre-main sequence -- ISM: jets and outflows

Offprint request: M. Takami, takami@star.herts.ac.uk

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