Letter to the Editor

Herschel-ATLAS: The dust energy balance in the edge-on spiral galaxy UGC 4754 ^*

¹ Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, 9000 Gent, Belgium e-mail: maarten.baes@ugent.be
² European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
³ School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, UK
⁴ Department of Physics, University of Crete, PO Box 2208, 71003 Heraklion, Greece
⁵ Dept. of Physics & Astronomy, University of California, Irvine, CA 92697, USA
⁶ School of Physics and Astronomy, Cardiff University, The Parade, Cardiff, CF24 3AA, UK
⁷ Astrophysics Group, Imperial College, Blackett Laboratory, Prince Consort Road, London SW7 2AZ, UK
⁸ Centre for Astrophysics Research, Science and Technology Research Centre, University of Hertfordshire, Herts AL10 9AB, UK

⁹ Laboratoire d'Astrophysique de Marseille, UMR6110 CNRS, 38 Rue F. Joliot-Curie, 13388 Marseille, France
¹⁰ INAF - Osservatorio Astronomico di Padova, Vicolo Osservatorio 5, 35122 Padova, Italy
¹¹ Instituto de Astrofísica de Canarias, C/Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain
¹² Departamento de Astrofísica, Universidad de La Laguna (ULL), 38205 La Laguna, Tenerife, Spain

¹³ Scuola Internazionale Superiore di Studi Avanzati, via Beirut 2–4, 34151 Triest, Italy
¹⁴ Infrared Processing and Analysis Center, California Institute of Technology, 770 South Wilson Av, Pasadena, CA 91125, USA
¹⁵ Instituto de Física de Cantabria (CSIC-UC), Santander, 39005, Spain
¹⁶ UK Astronomy Technology Center, Royal Observatory Edinburgh, Edinburgh, EH9 3HJ, UK
¹⁷ Institut d'Astrophysique Spatiale (IAS), Bâtiment 121, 91405 Orsay, France
¹⁸ Université Paris-Sud 11 and CNRS (UMR 8617), France
¹⁹ Astrophysics Branch, NASA Ames Research Center, Mail Stop 245-6, Moffett Field, CA 94035, USA
²⁰ Dept. of Physics and Astronomy, The Open University, Milton Keynes, MK7 6AA, UK
²¹ Scottish Universities Physics Alliance, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3HJ, UK
²² University of Padova, Department of Astronomy, Vicolo Osservatorio 3, 35122 Padova, Italy
²³ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
²⁴ Oxford Astrophysics, Denys Wilkinson Building, University of Oxford, Keble Road, Oxford, OX1 3RH, UK

Received: 31 March 2010
Accepted: 7 April 2010

Abstract

We use Herschel PACS and SPIRE observations of the edge-on spiral galaxy UGC 4754, taken as part of the H-ATLAS SDP observations, to investigate the dust energy balance in this galaxy. We build detailed SKIRT radiative models based on SDSS and UKIDSS maps and use these models to predict the far-infrared emission. We find that our radiative transfer model underestimates the observed FIR emission by a factor of two to three. Similar discrepancies have been found for other edge-on spiral galaxies based on IRAS, ISO, and SCUBA data. Thanks to the good sampling of the SED at FIR wavelengths, we can rule out an underestimation of the FIR emissivity as the cause for this discrepancy. Instead we support highly obscured star formation that contributes little to the optical extinction as a more probable explanation.