Starburst and cirrus models for submillimeter galaxies
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We present radiative transfer models for submillimeter galaxies with spectroscopic redshifts and mid-infrared spectroscopy from Spitzer/TRS and analyze available Spitzer/MIPS 24, 70 and 160 μm data. We use two types of starburst models, a cirrus model and a model for the emission of an AGN torus in order to investigate the nature of mese objects. We find mat for three of the objects (25%) cirrus emission alone can account for the mid-infrared spectrum and the MIPS and submillimeter data. For the remaining objects we find that we need a combination of starburst and cirrus in order to fit simultaneously the multi-wavelength data. We find that the typical submillimeter galaxy has comparable luminosity in the starburst (median L = 1012.5 L ⊙) and cirrus (median L = 1012.4 L⊙;) components. This could arise if the galaxies have been forming stars continuously for the last 250 Myr with the star formation occurring in the last 5 Myr being shrouded by high-optical-depth molecular cloud dust, whereas the rest of the starlight is attenuated by diffuse dust or cirrus with an A v of about 1 mag.