The SCUBA Local Universe Galaxy Survey I: First Measurements of the Submillimetre Luminosity and Dust Mass Functions

TL;DR

This study uses SCUBA to measure submillimetre emission from a complete galaxy sample, deriving luminosity and dust mass functions, and exploring correlations with galaxy properties, revealing higher gas-to-dust ratios than in the Milky Way.

Contribution

First measurements of submillimetre luminosity and dust mass functions for a complete galaxy sample, providing new insights into dust properties and galaxy correlations.

Findings

Luminosity and dust mass functions fit by Schechter functions.

Average gas-to-dust ratio is 581, higher than Galactic value.

Strong correlation between dust mass and molecular hydrogen mass.

Abstract

We have used SCUBA to observe a complete sample of 104 galaxies selected at 60 microns from the IRAS BGS and we present here the 850 micron measurements. Fitting the 60,100 and 850 micron fluxes with a single temperature dust model gives the sample mean temperature T=36 K and beta = 1.3. We do not rule out the possibility of dust which is colder than this, if a 20 K component was present then our dust masses would increase by factor 1.5-3. We present the first measurements of the luminosity and dust mass functions, which were well fitted by Schechter functions (unlike those 60 microns). We have correlated many global galaxy properties with the submillimetre and find that there is a tendancy for less optically luminous galaxies to contain warmer dust and have greater star formation efficiencies (cf. Young 1999). The average gas-to-dust ratio for the sample is 581 +/- 43 (using both atomic and molecular hydrogen), significantly higher than the Galactic value of 160. We believe this discrepancy is due to a cold dust component at T < 20 K. There is a suprisingly tight correlation between dust mass and the mass of molecular hydrogen as estimated from CO measurements, with an intrinsic scatter of ~50%.