Letter to the Editor

Dust, Ice, and Gas In Time (DIGIT) Herschel program first results^*

A full PACS-SED scan of the gas line emission in protostar DK Chamaeleontis

¹ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 78, Cambridge, MA 02138, USA e-mail: tvankempen@cfa.harvard.edu
² The University of Texas at Austin, Department of Astronomy, 1 University Station C1400, Austin, Texas 78712-0259, USA
³ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
⁴ Max-Planck-Institut für extraterrestriche Physik. Garching, Germany
⁵ Herschel Science Centre, European Space Astronomy Centre (ESA), PO Box 78, 28691 Villanueva de la Cañada (Madrid), Spain
⁶ Department of Astronomy and Space Science, Astrophysical Research Center for the Structure and Evolution of the Cosmos, Sejong University, Seoul 143-747, Republic of Korea
⁷ Centre for Star and Planet Formation, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen K., Denmark
⁸ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁹ Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
¹⁰ (Postdoctoral Fellow of the Fund for Scientific Research, Flanders, Belgium)
¹¹ Astronomy Department, University of California, Berkeley, CA 94720, USA
¹² Laboratoire d'Astrophysique de Grenoble, CNRS/Université Joseph Fourier (UMR5571) BP 53, 38041 Grenoble Cedex 9, France
¹³ Department of Astronomy, The University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042, USA
¹⁴ Caltech, Division of Geological & Planetary Sciences, Mail Code 150-21, Pasadena, CA 91125
¹⁵ Naval Research Laboratory, Code 7211, Washington, DC 20375, USA
¹⁶ Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822, USA ; Spitzer Fellow
¹⁷ Astronomical Institute “Anton Pannekoek”, University of Amsterdam, PO Box 94249, 1090 GE Amsterdam, The Netherlands
¹⁸ Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010 6500 GL Nijmegen, The Netherlands
¹⁹ Institut für Theoretische Astrophysik, Universitt Heidelberg, Albert-Ueberle-Strasse 2, 69120 Heidelberg, Germany
²⁰ University of Vienna, Department of Astronomy, Türkenschanzstr. 17, 1180 Vienna, Austria
²¹ Department of Astronomy, University of Maryland, College Park, MD 20742, USA
²² Dpt. de Física Teórica, Fac. de Ciencias, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
²³ SRON Netherlands Institute for Space Research, PO Box 800, 9700 AV, Groningen, The Netherlands
²⁴ National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ 85719, USA

Received: 31 March 2010
Accepted: 14 May 2010

Abstract

Aims. We aim to study the composition and energetics of the circumstellar material of DK Cha, an intermediate-mass star in transition from an embedded configuration to a star plus disk stage, during this pivotal stage of its evolution.

Methods. Using the range scan mode of PACS on the Herschel Space Observatory, we obtained a spectrum of DK Cha from 55 to 210 μm as part of the DIGIT key program.

Results. Almost 50 molecular and atomic lines were detected, many more than the 7 lines detected in ISO-LWS. Nearly the entire ladder of CO from J = 14–13 to 38–37 (E_u/k = 4080 K), water from levels as excited as = 7₀₇ (E_u/k = 843 K), and OH lines up to E_u/k = 290 K were detected.

Conclusions. The continuum emission in our PACS SED scan matches the flux expected by a model consisting of a star, a surrounding disk of 0.03 , and an envelope of a similar mass, supporting the suggestion that the object is emerging from its main accretion stage. Molecular, atomic, and ionic emission lines in the far-infrared reveal the outflow's influence on the envelope. The inferred hot gas may be photon-heated, but some emission may be caused by C-shocks in the walls of the outflow cavity.