Letter to the Editor
First results of the Herschel key program “Dust, Ice and Gas In Time” (DIGIT): Dust and gas spectroscopy of HD 100546 *
Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany e-mail: email@example.com
2 The University of Texas at Austin, Department of Astronomy, 1 University Station C1400, Austin, Texas 78712-0259, USA
3 Instituut voor Sterrenkunde, K.U.Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
4 Astronomical Institute “Anton Pannekoek”, University of Amsterdam, PO Box 94249, 1090 GE Amsterdam, The Netherlands
5 SRON Netherlands Institute for Space Research, PO Box 800, 9700 AV, Groningen, The Netherlands
6 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
7 Max Planck Institut für extraterrestrische Physik, Garching, Germany
8 Dpt. de Física Teórica, Fac. de Ciencias, Universidad Autónoma de Madrid, Campus Cantoblanco, 28049 Madrid, Spain
9 Laboratoire d'Astrophysique de Grenoble, CNRS/Université Joseph Fourier (UMR5571) BP 53, 38041 Grenoble Cedex 9, France
10 National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ 85719, USA
11 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 42, Cambridge, MA 02138, USA
12 Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010 6500 GL Nijmegen, The Netherlands
13 Naval Research Laboratory, Code 7211, Washington, DC 20375, USA
14 Department of Astronomy, The University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042, USA
15 Caltech, Division of Geological & Planetary Sciences, Mail Code 150-21, Pasadena, CA 91125, USA
16 Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822, USA
17 Astronomy Department, University of California, Berkeley, CA 94720, USA
18 University of Vienna, Department of Astronomy, Türkenschanzstr. 17, 1180 Vienna, Austria
19 Centre for Star and Planet Formation, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen K., Denmark
20 Department of Astronomy, University of Maryland, College Park, MD 20742, USA
21 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
22 Herschel Science Centre, European Space Astronomy Centre (ESA), PO Box 78, 28691 Villanueva de la Cañada (Madrid), Spain
Accepted: 28 April 2010
Context. We present far-infrared spectroscopic observations, taken with the Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory, of the protoplanetary disk around the pre-main-sequence star HD 100546. These observations are the first within the DIGIT Herschel key program, which aims to follow the evolution of dust, ice, and gas from young stellar objects still embedded in their parental molecular cloud core, through the final pre-main-sequence phases when the circumstellar disks are dissipated.
Aims. Our aim is to improve the constraints on temperature and chemical composition of the crystalline olivines in the disk of HD 100546 and to give an inventory of the gas lines present in its far-infrared spectrum.
Methods. The 69 μm feature is analyzed in terms of position and shape to derive the dust temperature and composition. Furthermore, we detected 32 emission lines from five gaseous species and measured their line fluxes.
Results. The 69 μm emission comes either from dust grains with ~70 K at radii larger than 50 AU, as suggested by blackbody fitting, or it arises from ~200 K dust at ~13 AU, close to the midplane, as supported by radiative transfer models. We also conclude that the forsterite crystals have few defects and contain at most a few percent iron by mass. Forbidden line emission from [C ii] at 157 μm and [O i] at 63 and 145 μm, most likely due to photodissociation by stellar photons, is detected. Furthermore, five H2O and several OH lines are detected. We also found high-J rotational transition lines of CO, with rotational temperatures of ~300 K for the transitions up to J = 22–21 and T ~ 800 K for higher transitions.
Key words: stars: individual: HD 100546 / infrared: general / stars: pre-main sequence / techniques: spectroscopic
© ESO, 2010