Letter to the Editor

The Herschel Space Observatory view of dust in M81

¹ Astrophysics Group, Imperial College, Blackett Laboratory, Prince Consort Road, London SW7 2AZ, UK e-mail: g.bendo@imperial.ac.uk
² Dept. of Physics & Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1, Canada
³ School of Physics and Astronomy, Cardiff University, Queens Buildings The Parade, Cardiff CF24 3AA, UK
⁴ Laboratoire AIM, CEA/DSM – CNRS – Université Paris Diderot, Irfu/Service d'Astrophysique, 91191 Gif-sur-Yvette, France
⁵ Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, 9000 Gent, Belgium
⁶ Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
⁷ Jet Propulsion Laboratory, Pasadena, CA 91109, United States; Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA
⁸ Laboratoire d'Astrophysique de Marseille, UMR6110 CNRS, 38 Rue F. Joliot-Curie, 13388 Marseille, France
⁹ Instituto de Astrofisica de Canarias, C/vía Láctea s/n, 38200 La Laguna, Spain
¹⁰ Institut d'Astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, 98 bis Boulevard Arago, 75014 Paris, France
¹¹ Department of Physics & Astronomy, University of California, Irvine, CA 92697, USA
¹² Observational Cosmology Lab, Code 665, NASA Goddard Space Flight Center Greenbelt, MD 20771, USA
¹³ Department of Astrophysical & Planetary Sciences, CASA CB-389, University of Colorado, Boulder, CO 80309, USA
¹⁴ ESA Astrophysics Missions Division, ESTEC, PO Box 299, 2200 AG Noordwijk, The Netherlands
¹⁵ Astronomy Centre, Department of Physics and Astronomy, University of Sussex, UK
¹⁶ Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK
¹⁷ School of Physics & Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, UK
¹⁸ Istituto di Fisica dello Spazio Interplanetario, INAF, via del Fosso del Cavaliere 100, 00133 Roma, Italy
¹⁹ Infrared Processing and Analysis Center, California Institute of Technology, Mail Code 100-22, 770 South Wilson Av, Pasadena, CA 91125, USA
²⁰ Centre for Astrophysics Research, Science and Technology Research Centre, University of Hertfordshire, College Lane, Herts AL10 9AB, UK
²¹ University of Padova, Department of Astronomy, Vicolo Osservatorio 3, 35122 Padova, Italy
²² Observatoire Astronomique de Strasbourg, UMR 7550 Université de Strasbourg – CNRS, 11 rue de l'Université, 67000 Strasbourg, France
²³ UK Astronomy Technology Center, Royal Observatory Edinburgh, Edinburgh, EH9 3HJ, UK
²⁴ Institut für Astronomie, Universität Wien, Türkenschanzstr. 17, 1180 Wien, Austria

Received: 30 March 2010
Accepted: 20 April 2010

Abstract

We use Herschel Space Observatory data to place observational constraints on the peak and Rayleigh-Jeans slope of dust emission observed at 70–500 μm in the nearby spiral galaxy M81. We find that the ratios of wave bands between 160 and 500 μm are primarily dependent on radius but that the ratio of 70 to 160 μm emission shows no clear dependence on surface brightness or radius. These results along with analyses of the spectral energy distributions imply that the 160–500 μm emission traces 15–30 K dust heated by evolved stars in the bulge and disc whereas the 70 μm emission includes dust heated by the active galactic nucleus and young stars in star forming regions.