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Issue A&A
Volume 454, Number 2, August I 2006
APEX Special Booklet
Page(s) L75 - L78
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20065336



A&A 454, L75-L78 (2006)
DOI: 10.1051/0004-6361:20065336

Letter

Warm molecular gas in the envelope and outflow of IRAS 12496-7650 (DK Chamaeleontis)

T. A. van Kempen1, M. R. Hogerheijde1, E. F. van Dishoeck1, R. Güsten2, P. Schilke2 and L.-Å. Nyman3

1  Leiden Observatory, Leiden University Niels Bohrweg 2, 2333 CA, Leiden, The Netherlands
    e-mail: kempen@strw.leidenuniv.nl
2  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
3  European Southern Observatory, Casille 19001, Santiago, Chile

(Received 31 March 2006 / Accepted 9 May 2006)

Abstract
Aims.To obtain insight into the physical structure of the warm gas in the inner envelope of protostars and the interaction with the outflow.
Methods.Sub-millimeter observations of 12CO, 13CO and/or C18O in J=3-2, J=4-3 and J=7-6 were obtained with the APEX Telescope towards IRAS 12496-7650, an intermediate mass young stellar object. The data are compared to ISO-LWS observations of CO J=14-13 up to J=19-18 lines to test the different proposed origins of the CO lines.
Results.The outflow is prominently detected in the 3-2 and 4-3 lines, but not seen at similar velocities in the 7-6 line, constraining the temperature in the high-velocity (>5 km s-1 from line center) gas to less than 50 K, much lower than inferred from the analysis of the ISO-LWS data. In addition, no isothermal gas model can reproduce the emission in both the 7-6 and the higher-J ISO-LWS lines. The 7-6 line probably originates in the inner (<250 AU) region of the envelope at ~150 K. Detailed radiative transfer calculations suggest that the ISO-LWS lines are excited by a different mechanism, possibly related to the larger-scale outflow. All possible mechanisms on scales smaller than 8'' are excluded. High-resolution continuum as well as high-J 12CO and isotopic line mapping are needed to better constrain the structure of the warm gas in the inner envelope and the interaction with the outflow.


Key words: circumstellar matter -- stars: pre-main sequence -- stars: formation -- submillimeter



© ESO 2006


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