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We investigate the multi-wavelength properties of a sample of 450-µm selected sources from the SCUBA-2 Cosmology Legacy Survey (S2CLS). A total of 69 sources were identified above 4σ in deep SCUBA-2 450-µm observations overlapping the UDS and COSMOS fields and covering 210 arcmin 2 to a typical depth of σ 450 = 1.5 mJy. Reliable cross identification are found for 58 sources (84 per cent) in Spitzer and Hubble Space Telescope WFC3/IR data. The photometric redshift distribution (dN/dz) of 450 µm-selected sources is presented, showing a broad peak in the redshift range 1 < z < 3, and a median of z = 1.4. Combining the SCUBA-2 photometry with Herschel SPIRE data from HerMES, the submm spectral energy distribution (SED) is examined via the use of modified blackbody fits, yielding aggregate values for the IR luminosity, dust temperature and emissivity of L IR = 10 12±0.8 L ⊙ , T D = 42 ± 11 K and β D = 1.6 ± 0.5, respectively. The relationship between these SED parameters and the physical properties of galaxies is investigated, revealing correlations between T D and L IR and between β D and both stellar mass and effective radius. The connection between star formation rate and stellar mass is explored, with 24 per cent of 450 µm sources found to be "star-bursts", i.e. displaying anomalously high specific SFRs. However, both the number density and observed properties of these "star-burst" galaxies are found consistent with the population of normal star-forming galaxies. c 2013 RAS 2 I.G. Roseboom et al.

The first deep blank-field 450µm map (1σ ≈ 1.3 mJy) from the SCUBA-2 Cosmology Legacy Survey (S2CLS), conducted with the James Clerk Maxwell Telescope (JCMT) is presented. Our map covers 140 arcmin 2 of the Cosmological Evolution Survey (COSMOS) field, in the footprint of the Hubble Space Telescope (HST) Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS). Using 60 submillimetre galaxies (SMGs) detected at 3.75σ, we evaluate the number counts of 450µm-selected galaxies with flux densities S 450 > 5 mJy. The 8 ′′ JCMT beam and high sensitivity of SCUBA-2 now make it possible to directly resolve a larger fraction of the cosmic infrared background (CIB, peaking at λ ∼ 200µm) into the individual galaxies responsible for its emission than has previously been possible at this wavelength. At S 450 > 5 mJy we resolve (7.4 ± 0.7) × 10 −2 MJy sr −1 of the CIB at 450µm (equivalent to 16 ± 7% of the absolute brightness measured by the Cosmic Background Explorer at this wavelength) into point sources. A further ∼40% of the CIB can be recovered through a statistical stack of 24µm emitters in this field, indicating that the majority (≈60%) of the CIB at 450µm is emitted by galaxies with S 450 > 2 mJy. The average redshift of 450µm emitters identified with an optical/near-infrared counterpart is estimated to be z = 1.3, implying that the galaxies in the sample are in the ultraluminous class (L IR ≈ 1.1 × 10 12 L ⊙ ). If the galaxies contributing to the statistical stack lie at similar redshifts, then the majority of the CIB at 450µm is emitted by galaxies in the LIRG class with L IR > 3.6 × 10 11 L ⊙ .

MS 0451.6−0305 is a rich galaxy cluster whose strong lensing is particularly prominent at submm wavelengths. We combine new SCUBA-2 data with imaging from Herschel SPIRE and PACS and HST in order to try to understand the nature of the sources being lensed. In the region of the "giant submm arc," we uncover seven multiply imaged galaxies (up from the previously known three), of which six are found to be at a redshift of z ∼ 2.9, and possibly constitute an interacting system. Using a novel forward-modelling approach, we are able to simultaneously deblend and fit SEDs to the individual galaxies that contribute to the giant submm arc, constraining their dust temperatures, far infrared luminosities and star formation rates. The submm arc first identified by SCUBA can now be seen to be composed of at least five distinct sources, four of these within the galaxy group at z ∼ 2.9. The total unlensed luminosity for this galaxy group is (3.1 ± 0.3) × 10 12 L , which gives an unlensed star formation rate of (450 ± 50) M yr −1 . From the properties of this system, we see no evidence of evolution towards lower temperatures in the dust temperature versus far-infrared luminosity relation for high redshift galaxies.

We present SCUBA-2 follow-up of 61 candidate high-redshift Planck sources. Of these, 10 are confirmed strong gravitational lenses and comprise some of the brightest such submm sources on the observed sky, while 51 are candidate proto-cluster fields undergoing massive starburst events. With the accompanying Herschel-SPIRE observations and assuming an empirical dust temperature prior of 34 +13 −9 K, we provide photometric redshift and far-IR luminosity estimates for 172 SCUBA-2-selected sources within these Planck overdensity fields. The redshift distribution of the sources peak between a redshift of 2 and 4, with one third of the sources having S 500 /S 350 > 1. For the majority of the sources, we find far-IR luminosities of approximately 10 13 L ⊙ , corresponding to star-formation rates of around 1000 M ⊙ yr −1 . For S 850 > 8 mJy sources, we show that there is up to an order of magnitude increase in star-formation rate density and an increase in uncorrected number counts of 6 for S 850 > 8 mJy when compared to typical cosmological survey fields. The sources detected with SCUBA-2 account for only approximately 5 per cent of the Planck flux at 353 GHz, and thus many more fainter sources are expected in these fields.

For high-redshift submillimetre or millimetre sources detected with single dish telescopes, interferometric follow-up has shown that many are multiple submm galaxies blended together. Confusion-limited Herschel observations of such targets are also available, and these sample the peak of their spectral energy distribution in the farinfrared. Many methods for analysing these data have been adopted, but most follow the traditional approach of extracting fluxes before model spectral energy distributions are fit, which has the potential to erase important information on degeneracies among fitting parameters and glosses over the intricacies of confusion noise. Here, we adapt the forward-modelling method that we originally developed to disentangle a high-redshift strongly-lensed galaxy group, in order to tackle this problem in a more statistically rigorous way, by combining source deblending and SED fitting into the same procedure. We call this method "SEDeblend." As an application, we derive constraints on farinfrared luminosities and dust temperatures for sources within the ALMA follow-up of the LABOCA Extended Chandra Deep Field South Submillimetre Survey. We find an average dust temperature for an 870 µm-selected sample of (33.9±2.4) K for the full survey. When selection effects of the sample are considered, we find no evidence that the average dust temperature evolves with redshift.

Planck intermediate results XXVII. High-redshift infrared galaxy overdensity candidates and lensed sources discovered by Planck and confirmed by Herschel-SPIRE