Far-infrared colours of nearby late-type galaxies in the Herschel Reference Survey^⋆,⋆⋆

¹ Laboratoire d’Astrophysique de Marseille – LAM, Université d’Aix-Marseille & CNRS, UMR7326, 38 rue F. Joliot-Curie, 13388 Marseille Cedex 13, France
e-mail: Alessandro.Boselli@oamp.fr; Laure.Ciesla@oamp.fr; Veronique.Buat@oamp.fr; Mederic.Boquien@oamp.fr; Samuel.Boissier@oamp.fr
² European Southern Observatory, Karl-Schwarzschild Str. 2, 85748 Garching bei Muenchen, Germany
e-mail: lcortese@eso.org
³ UK ALMA Regional Centre Node, Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M139 PL, UK
e-mail: george.bendo@manchester.ac.uk
⁴ School of Physics and Astronomy, Cardiff University, Queens Buildings The Parade, Cardiff CF24 3AA, UK
e-mail: Steve.Eales@astro.cf.ac.uk; Michael.Pohlen@astro.cf.ac.uk; Matthew.Smith@astro.cf.ac.uk; Jonathan.Davies@astro.cf.ac.uk; Walter.Gear@astro.cf.ac.uk
⁵ Universita’ di Milano-Bicocca, piazza della Scienza 3, 20100 Milano, Italy
e-mail: giuseppe.gavazzi@mib.infn.it
⁶ Kavli Institute for Astronomy & Astrophysics, Peking University, Beijing 100871, PR China
e-mail: tmhughes@pku.edu.cn
⁷ Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, 9000 Gent, Belgium
e-mail: maarten.baes@ugent.be
⁸ INAF – Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
e-mail: sbianchi@arcetri.astro.it; laura@arcetri.astro.it
⁹ Astrophysics Group, Imperial College, Blackett Laboratory, Prince Consort Road, London SW7 2AZ, UK
e-mail: d.clements@imperial.ac.uk
¹⁰ Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA ; California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA
e-mail: acooray@uci.edu
¹¹ CEA/DSM/IRFU/Service d’Astrophysique, CEA, Saclay, Orme des Merisiers, Bâtiment 709, 91191 Gif-sur-Yvette, France
e-mail: pasquale.panuzzo@cea.fr; aurelie.remy@cea.fr
¹² INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica, via Fosso del Cavaliere 100, 00133 Roma, Italy
e-mail: luigispinoglio@gmail.com
¹³ Dark Cosmology Centre, Niels Bohr Institute – University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
e-mail: zibetti@dark-cosmology.dk

Received: 7 December 2011
Accepted: 10 January 2012

Abstract

We study the far infrared (60–500 μm) colours of late-type galaxies in the Herschel Reference Survey, a K-band selected, volume limited sample of nearby galaxies. The far infrared colours are correlated with each other, with tighter correlations for the indices that are closer in wavelength. We also compare the different colour indices to various tracers of the physical properties of the target galaxies, such as the surface brightness of the ionising and non-ionising stellar radiation, the dust attenuation and the metallicity. The emission properties of the cold dust dominating the far infrared spectral domain are regulated by the properties of the interstellar radiation field. Consistent with that observed in nearby, resolved galaxies, our analysis shows that the ionising and the non-ionising stellar radiation, including that emitted by the most evolved, cold stars, both contribute to the heating of the cold dust component. This work also shows that metallicity is another key parameter characterising the cold dust emission of normal, late-type galaxies. A single modified black body with a grain emissivity index β = 1.5 better fits the observed SPIRE flux density ratios S250/S350 vs. S350/S500 than β = 2, although values of β ≃ 2 are possible in metal rich, high surface brightness galaxies. Values of β ≲ 1.5 better represent metal poor, lowsurface brightness objects. This observational evidence provides strong constraints for dust emission models of normal, late type galaxies.