Abstract
We combine Planck HFI data at 857, 545, 353 & 217GHz with data from WISE,
Spitzer, IRAS & Herschel to investigate the properties of a flux limited sample
of local star-forming galaxies. A 545GHz flux density limit was chosen so that
the sample is 80% complete at this frequency, giving a sample of 234 local
galaxies. We investigate the dust emission and star formation properties of the
sample via various models & calculate the local dust mass function. Although
1-component modified black bodies fit the dust emission longward of 80um very
well (median beta=1.83) the degeneracy between dust temp & beta also means that
the SEDs are very well described by a dust emissivity index fixed at beta=2 and
10<T<25 K. Although a second, warmer dust component is required to fit shorter
wavelength data, & contributes ~1/3 of the total infrared emission, its mass is
negligible. No evidence is found for a very cold (6-10 K) dust component. The
temp of the cold dust component is strongly influenced by the ratio of the star
formation rate to the total dust mass. This implies, contrary to what is often
assumed, that a significant fraction of even the emission from ~20 K dust is
powered by ongoing star formation, whether or not the dust itself is associated
with star forming clouds or `cirrus'. There is statistical evidence of a
free-free contribution to the 217GHz flux densities of <20%. We find a median
dust-to-stellar mass ratio of 0.0046; & that this ratio is anti-correlated with
galaxy mass. There is good correlation between dust mass & atomic gas mass
(median M_d/M_HI = 0.022), suggesting that galaxies that have more dust have
more interstellar medium in general. Our derived dust mass function implies a
mean dust mass density of the local Universe (for dust within galaxies), of
7.0+-1.4 x 10^5 M_solar/Mpc, significantly greater than that found in the most
recent estimate using Herschel data.
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