Dust and star-formation properties of a complete sample of local galaxies drawn from the Planck Early Release Compact Source Catalogue

TL;DR

This study combines multi-wavelength data to analyze dust and star formation in local galaxies, revealing the dust properties, mass function, and the relationship between dust, gas, and star formation activity.

Contribution

It provides a comprehensive analysis of dust emission and star formation properties in a complete local galaxy sample using Planck and other infrared data, including the dust mass function.

Findings

1-component black body fits dust emission well longward of 80um

Warm dust contributes ~1/3 of infrared emission but has negligible mass

No evidence for very cold dust (6-10 K) in the sample

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.