Volume 518, July-August 2010
Herschel: the first science highlights
|Number of page(s)||5|
|Published online||16 July 2010|
Letter to the Editor
Max-Planck-Institut für Sonnensystemforschung, 37191 Katlenburg-Lindau, Germany
2 LESIA, Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon, France
3 California Institute of Technology, Pasadena, CA 91125, USA
4 Space Research Centre, Polish Academy of Sciences, Warsaw, Poland
5 DLR, German Aerospace Centre, Bonn-Oberkassel, Germany
6 Institute d'Astrophysique et de Geophysique, Université de Liège, Belgium
7 Rosetta Science Operations Centre, European Space Astronomy Centre, European Space Agency, Spain
8 Instituto de Astrofísica de Andalucía (CSIC), Spain
9 Space Science & Technology Department, Rutherford Appleton Laboratory, UK
10 Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Belgium
11 Astronomy Department, University of Michigan, USA
12 Laboratory of Molecular Astrophysics, CAB-CSIC, INTA, Spain
13 Sterrenkundig Instituut Anton Pannekoek, University of Amsterdam, Science Park 904, 1098 Amsterdam, The Netherlands
14 LERMA, Observatoire de Paris, France
15 SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD, Groningen, The Netherlands
16 Leiden Observatory, University of Leiden, The Netherlands
17 Joint ALMA Observatory, Chile
18 Herschel Science Centre, European Space Astronomy Centre, European Space Agency, Spain
19 Department of Physics and Astronomy, University of Lethbridge, Canada
20 1st Physics Institute, University of Cologne, Germany
21 Physikalisches Institut, University of Bern, Switzerland
22 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
23 Chalmers University of Technology, 412 96 Göteborg, Sweden
24 Institute of Astronomy, ETH Zürich, 8093 Zürich, Switzerland
Accepted: 13 May 2010
High-resolution far-infrared and sub-millimetre spectroscopy of water lines is an important tool to understand the physical and chemical properties of cometary atmospheres. We present observations of several rotational ortho- and para-water transitions in comet C/2008 Q3 (Garradd) performed with HIFI on Herschel. These observations have provided the first detection of the 212–101 (1669 GHz) ortho and 111–000 (1113 GHz) para transitions of water in a cometary spectrum. In addition, the ground-state transition 110–101 at 557 GHz is detected and mapped. By detecting several water lines quasi-simultaneously and mapping their emission we can constrain the excitation parameters in the coma. Synthetic line profiles are computed using excitation models which include excitation by collisions, solar infrared radiation, and radiation trapping. We obtain the gas kinetic temperature, constrain the electron density profile, and estimate the coma expansion velocity by analyzing the map and line shapes. We derive water production rates of 1.7–2.8 × 1028 s-1 over the range rh = 1.83–1.85 AU.
Key words: comets: individual: C/2008 Q3 / radio lines: general / submillimeter: general / techniques: spectroscopic
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
Figure 5 is only available in electronic form at http://www.aanda.org
© ESO, 2010
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