The SCUBA Local Universe Galaxy Survey -- I. First measurements of the submillimetre luminosity and dust mass functions

Abstract

This is the first of a series of papers presenting results from the SCUBA Local Universe Galaxy Survey (SLUGS), the first statistical survey of the submillimetre properties of the local Universe. As the initial part of this survey, we have used the SCUBA camera on the James Clerk Maxwell Telescope to observe 104 galaxies from the IRAS Bright Galaxy Sample. We present here the 850‐μm flux measurements. The 60‐, 100‐, and 850‐μm flux densities are well fitted by single‐temperature dust spectral energy distributions, with the sample mean and standard deviation for the best‐fitting temperature being Td=35.6±4.9 K and for the dust emissivity index β=1.3±0.2. The dust temperature was found to correlate with 60‐μm luminosity. The low value of β may simply mean that these galaxies contain a significant amount of dust that is colder than these temperatures. We have estimated dust masses from the 850‐μm fluxes and from the fitted temperature, although if a colder component at around 20 K is present (assuming a β of 2), then the estimated dust masses are a factor of 1.5–3 too low. We have made the first direct measurements of the submillimetre luminosity function (LF) and of the dust mass function. Unlike the IRAS 60‐μm LF, these are well fitted by Schechter functions. The slope of the 850‐μm LF at low luminosities is steeper than −2, implying that the LF must flatten at luminosities lower than we probe here. We show that extrapolating the 60‐μm LF to 850 μm using a single temperature and β does not reproduce the measured submillimetre LF. A population of ‘cold’ galaxies (Td<25 K) emitting strongly at submillimetre wavelengths would have been excluded from the 60‐μm‐selected sample. If such galaxies do exist, then this estimate of the 850‐μm flux is biased (it is underestimated). Whether such a population does exist is unknown at present. We correlate many of the global galaxy properties with the FIR/submillimetre properties. We find that there is a tendency for less luminous galaxies to contain hotter dust and to have a greater star formation efficiency (cf. Young). The average gas‐to‐dust ratio for the sample is 581±43 (using both the atomic and molecular hydrogen), which is significantly higher than the Galactic value of 160. We believe that this discrepancy is probably due to a ‘cold dust’ component at Td≤20 K in our galaxies. There is a surprisingly tight correlation between dust mass and the mass of molecular hydrogen, estimated from CO measurements, with an intrinsic scatter of ≃50 per cent.

Herschel-ATLAS: Dust temperature and redshift distribution of SPIRE and PACS detected sources using submillimetre colours

“…The large expected sample of sources from the 550 deg 2 of H-ATLAS will enable more detailed studies in the future, without the biases associated with selections of various sub-samples, including our own. While we show results here with β = 1.5 fixed, when fitting for β and T d we found β = 1.4 ± 0.1, consistent with β = 1.3 found in Dunne et al (2000).…”

“…2, we summarize our results and compare the H-ATLAS dust temperatures with dust temperatures in the literature for a variety of sub-mm bright galaxies. These samples are: (i) the sources in BLAST detected above 5σ in at least one of the BLAST bands with either a COMBO-17 (Wolf et al 2004) or a SWIRE photometric redshift (Rowan-Robinson et al 2008) and Spitzer-MIPS 70 and 160 μm fluxes (Dye et al 2009; β = 1.5 fixed); (ii) local ULIRGS observed with SCUBA at 450 and 850 μm and complemented with IRAS 60 and 100 μm fluxes ; β varied); (iii) SCUBA sub-mm galaxies detected at better than 3σ at 850 μm and having redshifts determined from Keck-I spectroscopy (Chapman et al 2005; β = 1.5 fixed); and (iv) local IRAS-selected galaxies with 60 and 100 μm fluxes complemented with SCUBA 850 μm (Dunne et al 2000; β varied).…”

Galaxy evolution and star formation efficiency at 0.2 < z < 0.6

“…where S νo is the observed FIR flux measured in Jy, D 2 Mpc is the luminosity distance in Mpc, B νr is the Planck function at the rest frequency νr = νo(1 + z), and we use a mass opacity coefficient of 25 cm 2 g −1 at rest-frame 100 μm (Hildebrand 1983;Dunne et al 2000;Draine 2003), with a frequency dependence of β = 1.5. Estimated dust masses are displayed in Table 3.…”

HERschelObservations of Edge-on Spirals (HEROES)

“…Soifer et al 1987;Dunne et al 2000;Pérez García & Rodríguez Espinosa 2001;Tuffs et al 2002;Draine et al 2007). This situation has changed substantially with the launch of the Herschel Space Observatory (Pilbratt et al 2010), which has a much improved spatial resolution and wider wavelength coverage than any of its predecessors.…”