Abstract
We present Herschel/PACS 100 and 160 micron integrated photometry for the 323 galaxies in the Herschel Reference Survey (HRS), a K-band-, volume-limited sample of galaxies in the local Universe. Once combined with the Herschel/SPIRE observations already available, these data make the HRS the largest representative sample of nearby galaxies with homogeneous coverage across the 100-500 micron wavelength range. In this paper, we take advantage of this unique dataset to investigate the properties and shape of the far-infrared/sub-millimeter spectral energy distribution in nearby galaxies. We show that, in the stellar mass range covered by the HRS (8<log(M*/Msun)<12), the far-infrared/sub-millimeter colours are inconsistent with a single modified black-body having the same dust emissivity index beta for all galaxies. In particular, either beta decreases, or multiple temperature components are needed, when moving from metal-rich/gas-poor to metal-poor/gas-rich galaxies. We thus investigate how the dust temperature and mass obtained from a single modified black-body depend on the assumptions made on beta. We show that, while the correlations between dust temperature, galaxy structure and star formation rate are strongly model dependent, the dust mass scaling relations are much more reliable, and variations of beta only change the strength of the observed trends.
Highlights
It is well established that approximately half of the radiative energy produced by galaxies is absorbed by dust grains and re-emitted in the infrared regime (Hauser & Dwek 2001; Boselli, Gavazzi & Sanvito 2003a; Dole et al 2006; Dale et al 2007; Burgarella et al 2013)
By using the same apertures on the Herschel Virgo Cluster Survey (HeViCS) maps reduced with both photProject and SCANAMORPHOS, we find that photProject maps provide flux densities ∼10 per cent lower than those obtained with SCANAMORPHOS, while no difference is seen at 100 μm
We presented PACS 100 and 160 μm integrated photometry for the Herschel Reference Survey (HRS)
Summary
It is well established that approximately half of the radiative energy produced by galaxies is absorbed by dust grains and re-emitted in the infrared regime (Hauser & Dwek 2001; Boselli, Gavazzi & Sanvito 2003a; Dole et al 2006; Dale et al 2007; Burgarella et al 2013). The first natural step in this direction is to quantify how the shape of the dust spectral energy distribution (SED) varies with galaxy properties across a wide range of morphological type, star formation activity, cold gas mass and metal content This is necessary to determine if the amount of radiation emitted at each wavelength is regulated by the intensity of the ISRF responsible for the dust heating or whether it retains an imprint of the chemical composition of the grains. Corresponding to the peak of the dust SED, the 100– 200 μm wavelength interval is crucial to properly quantify the shape of the SED, and to accurately determine the average dust temperature and total dust mass in galaxies These data make the HRS the largest representative sample of nearby galaxies with homogeneous coverage across the ∼100–500 μm wavelength range.
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