We presentHerschel -PACS spectroscopy of the [OI]63 μm far-infrared cooling line from a sample of six unlensed and spectroscopically-confirmed 87 0μm-selected submillimetre (submm) galaxies (SMGs) at 1.1 < z < 1.6 from the LABOCA Extended Chandra Deep Field South (ECDFS) Submm Survey (LESS). This is the first sur vey of [OI]63μm, one of the main photodissociation region (PDR) cooling lines, i n SMGs. New high-resolution ALMA interferometric 870μm continuum imaging confirms that these six Herschel -targeted SMG counterparts are bona fide sources of submm emission. We d etect [OI]63μm in two SMGs with a SNR> ∼ 3, tentatively detect [OI]63μm in one SMG, and constrain the line flux for the non-detections. We also exploit the combination of s ubmm continuum photometry from 250–870μm and our new PACS continuum measurements to constrain the fa r-infr red luminosity, LFIR, in these SMGs to. 30per cent. We find that SMGs do not show a deficit in their [OI]63μm–to–far-infrared (FIR) continuum luminosity ratios (wit h ratios ranging from ≃ 0.5–1.5 per cent), similar to what was seen previously for the [C II]158μm–to–FIR ratios in SMGs. These observed ratios are about an order of magnitud e higher than what is seen typically for local ultra luminous infrared galaxies (ULIRGs) , which adds to the growing body of evidence that SMGs are not simply ‘scaled up’ versions of l oca ULIRGs. Rather, the PDR line–to–LFIR ratios suggest that the star formation modes of SMGs are like ly more akin to that of local normal (lower-luminosity) star-forming gala xies, with the bulk of the star formation occurring in extended galaxy-scale ( ∼kpc) regions. These observations represent the first step towards a census of the major PDR cooling lines in typica l SMGs that will be attainable with ALMA, enabling detailed modelling to probe the global p ro erties of the star formation and the evolutionary status of SMGs.

We present a catalogue of ∼ 3000 submillimetre sources detected ( ≥ 3.5 σ ) at 850 µ m over ∼ 5 deg 2 surveyed as part of the James Clerk Maxwell Telescope (JCMT) SCUBA-2 Cosmology Legacy Survey (S2CLS). This is the largest survey of its kind at 850 µ m, increasing the sample size of 850 µ m selected submillimetre galaxies by an order of magnitude. The wide 850 µ m survey component of S2CLS covers the extragalactic fields: UKIDSS-UDS, COSMOS, Akari -NEP, Extended Groth Strip, Lockman Hole North, SSA22 and GOODS-North. The average 1 σ depth of S2CLS is 1.2 mJy beam − 1 , approaching the SCUBA-2 850 µ m confusion limit, which we determine to be σ c ≈ 0.8 mJy beam − 1 . We measure the 850 µ m number counts, reducing the Poisson errors on the differential counts to approximately 4 per cent at S 850 ≈ 3 mJy. With several independent fields, we investigate field-to-field variance, finding that the number counts on 0.5 ◦ –1 ◦ scales are generally within 50 per cent of the S2CLS mean for S 850 > 3 mJy, with scatter consistent with the Poisson and estimated cosmic variance uncertainties, although there is a marginal (2 σ ) density enhancement in GOODS-North. The observed counts are in reasonable agreement with recent phenomenological and semi-analytic models, although determining the shape of the faint-end slope ( S 850 < 3 mJy) remains a key test. The large solid angle of S2CLS allows us to measure the bright-end counts: at S 850 > 10 mJy there are approximately 10 sources per square and strongly lensed high-redshift galaxies. All calibrated maps and the catalogue are made publicly available.

We present a catalogue of ∼3000 submillimetre sources detected (≥3.5σ ) at 850 μm over ∼5 deg2 surveyed as part of the James Clerk Maxwell Telescope (JCMT) SCUBA-2 Cosmology Legacy Survey (S2CLS). This is the largest survey of its kind at 850 μm, increasing the sample size of 850 μm selected submillimetre galaxies by an order of magnitude. The wide 850 μm survey component of S2CLS covers the extragalactic fields: UKIDSS-UDS, COSMOS, Akari-NEP, Extended Groth Strip, Lockman Hole North, SSA22 and GOODS-North. The average 1σ depth of S2CLS is 1.2 mJy beam−1, approaching the SCUBA-2 850 μm confusion limit, which we determine to be σ c ≈ 0.8 mJy beam−1. We measure the 850 μm number counts, reducing the Poisson errors on the differential counts to approximately 4 per cent at S850 ≈ 3 mJy. With several independent fields, we investigate field-to-field variance, finding that the number counts on 0.5◦–1◦ scales are generally within 50 per cent of the S2CLS mean for S850 > 3 mJy, with scatter consistent with the Poisson and estimated cosmic variance uncertainties, although there is a marginal (2σ ) density enhancement in GOODS-North. The observed counts are in reasonable agreement with recent phenomenological and semi-analytic models, although determining the shape of the faint-end slope (S850 < 3 mJy) remains a key test. The large solid angle of S2CLS allows us to measure the bright-end counts: at S850 > 10 mJy there are approximately 10 sources per square degree, and we detect the distinctive up-turn in the number counts indicative of the detection of local sources of 850 μm emission, E-mail: j.geach@herts.ac.uk C © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society D ow naded rom http/academ ic.p.com /m nras/article-at/465/2/1789/2454739 by O en U niersity Lrary (ER ) user on 31 M ay 2019 1790 J. E. Geach et al. and strongly lensed high-redshift galaxies. All calibrated maps and the catalogue are made publicly available.

We present new, high-angular resolution interferometric observations with the Karl G. Jansky Very Large Array of 12CO J = 1−0 line emission and 4–8 GHz continuum emission in the strongly lensed, z = 2.3 submillimetre galaxy, SMM J21352-0102. Using these data, we identify and probe the conditions in ∼100 pc clumps within this galaxy, which we consider to be potential giant molecular cloud complexes, containing up to half of the total molecular gas in this system. In combination with far-infrared and submillimetre data, we investigate the far-infrared/radio correlation, measuring qIR = 2.39 ± 0.17 across SMM J21352. We search for variations in the properties of the interstellar medium (ISM) throughout the galaxy by measuring the spatially resolved qIR and radio spectral index, αradio, finding ranges qIR =[2.1, 2.6] and αradio = [−1.5, −0.7]. We argue that these ranges in αradio and qIR may reflect variations in the age of the ISM material. Using multi-J 12CO data, we quantitatively test a recent theoretical model relating the star formation rate surface density to the excitation of 12CO, finding good agreement between the model and the data. Lastly, we study the Schmidt–Kennicutt relation, both integrated across the system and within the individual clumps. We find small offsets between SMM J21352 and its clumps relative to other star-forming galaxy populations on the Schmidt–Kennicutt plot – such offsets have previously been interpreted as evidence for a bi-modal star formation law, but we argue that they can be equally well explained as arising due to a combination of observational uncertainties and systematic biases in the choice of model used to interpret the data.

We report the results of a deep SCUBA-2 850 and 450 mu m survey for dust-obscured ultra-luminous infrared galaxies (U/LIRGs) in the field of the z = 1.46 cluster XCS J2215.9-1738. We detect a striking overdensity of submillimeter sources coincident with the core of this cluster: similar to 3-4 x higher than expected in a blank field. We use the likely radio and mid-infrared counterparts to show that the bulk of these submillimeter sources have spectroscopic or photometric redshifts that place them in the cluster and that their multiwavelength properties are consistent with this association. The average far-infrared luminosities of these galaxies are (1.0 +/- 0.1) x 10(12) L-circle dot, placing them on the U/LIRG boundary. Using the total star formation occurring in the obscured U/LIRG population within the cluster, we show that the resulting mass-normalized star formation rate for this system supports previous claims of a rapid increase in star formation activity in cluster cores out to z similar to 1.5, which must be associated with the ongoing formation of the early-type galaxies that reside in massive clusters today.

We present high-resolution (0.″3) Atacama Large Millimeter Array 870 μm imaging of 52 sub-millimeter galaxies (SMGs) in the Ultra Deep Survey field to investigate the size and morphology of the sub-millimeter (sub-mm) emission on 2–10 kpc scales. We derive a median intrinsic angular size of FWHM = 0.″30 ± 0.″04 for the 23 SMGs in the sample detected at a signal-to-noise ratio (S/N) >10. Using the photometric redshifts of the SMGs we show that this corresponds to a median physical half-light diameter of 2.4 ± 0.2 kpc. A stacking analysis of the SMGs detected at S/N <10 shows they have sizes consistent with the 870 μm bright SMGs in the sample. We compare our results to the sizes of SMGs derived from other multi-wavelength studies, and show that the rest-frame ∼250 μm sizes of SMGs are consistent with studies of resolved 12CO (J = 3–2 to 7–6) emission lines, but that sizes derived from 1.4 GHz imaging appear to be approximately two times larger on average, which we attribute to cosmic ray diffusion. The rest-frame optical sizes of SMGs are around four times larger than the sub-millimeter sizes, indicating that the star formation in these galaxies is compact relative to the pre-existing stellar distribution. The size of the starburst region in SMGs is consistent with the majority of the star formation occurring in a central region, a few kiloparsecs in extent, with a median star formation rate surface density of 90 ± 30 M☉ yr−1 kpc−2, which may suggest that we are witnessing an intense period of bulge growth in these galaxies.

We analyze Hubble Space Telescope WFC3/H-160-band observations of a sample of 48 Atacama Large Millimeter/submillimeter Array detected submillimeter galaxies (SMGs) in the Extended Chandra Deep Field South field, to study their stellar morphologies and sizes. We detect 79% +/- 17% of the SMGs in the H-160-band imaging with a median sensitivity of 27.8 mag, and most (80%) of the nondetections are SMGs with 870 mu m fluxes of S-870 < 3 mJy. With a surface brightness limit of mu(H) similar to 26 mag arcsec(-2), we find that 82% +/- 9% of the H-160-band-detected SMGs at z = 1-3 appear to have disturbed morphologies, meaning they are visually classified as either irregulars or interacting systems, or both. By determining a Sersic fit to the H-160 surface brightness profiles, we derive a median Sersic index of n = 1.2 +/- 0.3 and a median half-light radius of re = 4.4(-0.5)(+1.1) kpc for our SMGs at z = 1-3. We also find significant displacements between the positions of the H160 component and 870 mu m emission in these systems, suggesting that the dusty starburst regions and less-obscured stellar distribution are not colocated. We find significant differences in the sizes and the Sersic index between our z = 2-3 SMGs and z similar to 2 quiescent galaxies, suggesting that a major transformation of the stellar light profile is needed in the quenching processes if SMGs are progenitors of the red-and-dead z similar to 2 galaxies. Given the short-lived nature of SMGs, we postulate that the majority of the z = 2-3 SMGs with S-870 greater than or similar to 2 mJy are early/mid-stage major mergers.

The ALESS survey has followed up on a sample of 122 sub-millimeter sources in the Extended Chandra Deep Field South at 870 mu m with the Atacama Large Millimeter Array (ALMA), allowing us to pinpoint the positions of sub-millimeter galaxies (SMGs) to similar to 0.3 arcsec and to find their precise counterparts at different wavelengths. This enabled the first compilation of the multi-wavelength spectral energy distributions (SEDs) of a statistically reliable survey of SMGs. In this paper, we present a new calibration of the MAGPHYS SED modeling code that is optimized to fit these ultraviolet-to-radio SEDs of z > 1 star-forming galaxies using an energy balance technique to connect the emission from stellar populations, dust attenuation, and dust emission in a physically consistent way. We derive statistically and physically robust estimates of the photometric redshifts and physical parameters (such as stellar masses, dust attenuation, star formation rates (SFRs), and dust masses) for the ALESS SMGs. We find that the ALESS SMGs have median stellar mass M-* = 8.9 +/- 0.1 x 10(10) M-circle dot, median SFR = 280 +/- 70 M-circle dot yr(-1), median overall V-band dust attenuation A(V) = 1.9 +/- 0.2 mag, median dust mass M-dust = (5.6 +/- 1.0) x 10(8) M-circle dot, and median average dust temperature T-dust similar or equal to 40 K. We find that the average intrinsic SED of the ALESS SMGs resembles that of local ultra-luminous infrared galaxies in the infrared range, but the stellar emission of our average SMG is brighter and bluer, indicating lower dust attenuation, possibly because they are more extended. We explore how the average SEDs vary with different parameters (redshift, sub-millimeter flux, dust attenuation, and total infrared luminosity), and we provide a new set of SMG templates that can be used to interpret other SMG observations. To put the ALESS SMGs into context, we compare their stellar masses and SFRs with those of less actively star-forming galaxies at the same redshifts. We find that at z similar or equal to 2, about half of the SMGs lie above the star-forming main sequence (with SFRs three times larger than normal galaxies of the same stellar mass), while half are consistent with being at the high-mass end of the main sequence. At higher redshifts (z similar or equal to 3.5), the SMGs tend to have higher SFRs and stellar masses, but the fraction of SMGs that lie significantly above the main sequence decreases to less than a third.

Carbon and oxygen isotope ratios are excellent measures of nuclear processing, but few such data have been taken toward extragalactic targets so far. Therefore, using the IRAM 30-m telescope, CN and CO isotopologues have been measured toward the nearby starburst galaxy NGC 253 and the prototypical ultraluminous infrared galaxy Mrk 231. Toward the center of NGC 253, the CN and (CN)-C-13 N = 1 -> 0 lines indicate no significant deviations from expected local thermodynamical equilibrium after accounting for moderate saturation effects (10 and 25%) in the two detected spectral components of the main species. Including calibration uncertainties, which dominate the error budget, the C-12/C-13 ratio becomes 40 +/- 10. This is larger than the ratio in the central molecular zone of the Galaxy, suggesting a higher infall rate of poorly processed gas toward the central region. Assuming that the ratio also holds for the CO emitting gas, this yields O-16/O-18 = 145 +/- 36 and O-16/O-17 = 1290 +/- 365 and a S-32/S-34 ratio close to the one measured for the local interstellar medium (2025). No indication of vibrationally excited CN is found in the lower frequency fine structure components of the N = 1 -> 0 and 2 -> 1 transitions at rms noise levels of 3 and 4 mK (15 and 20 mJy) in 8.5 km s-1 wide channels. Peak line intensity ratios between NGC 253 and Mrk 231 are similar to 100 for (CO)-C-12-O-16 and (CO)-C-12-O-18 J = 1 -> 0, while the ratio for (CO)-C-13-O-16 J = 1 -> 0 is similar to 250. This and similar (CO)-C-13 and (CO)-O-18 line intensities in the J = 1 -> 0 and 2 -> 1 transitions of Mrk 231 suggest C-12/C-13 similar to 100 and O-16/O-18 similar to 100, in agreement with values obtained for the less evolved ultraluminous merger Arp 220. Also, when accounting for other (scarcely available) extragalactic data, C-12/C-13 ratios appear to vary over a full order of magnitude, from >100 in ultraluminous high redshift galaxies to similar to 100 in more local such galaxies to similar to 40 in weaker starbursts that are not undergoing a large scale merger to 25 in the central molecular zone of the Milky Way. With C-12 being predominantly synthesized in massive stars, while C-13 is mostly ejected by longer lived lower mass stars at later times, this is qualitatively consistent with our results of decreasing carbon isotope ratios with time and rising metallicity. It is emphasized, however, that both infall of poorly processed material, initiating a nuclear starburst, and the ejecta from newly formed massive stars (in particular in the case of a top-heavy stellar initial mass function) can raise the carbon isotope ratio for a limited amount of time.

We present Submillimeter Array [ C II] 158 mu m and Karl G. Jansky Very Large Array (CO)-C-12(1-0) line emission maps for the bright, lensed, submillimeter source at z = 5.2430 behind A 773: HLSJ091828.6+514223 (HLS0918). We combine these measurements with previously reported line profiles, including multiple 12CO rotational transitions, [C II], water, and [N II], providing some of the best constraints on the properties of the interstellarmedium in a galaxy at z > 5. HLS0918 has a total far-infrared (FIR) luminosity L-FIR(8-1000 mu m) = (1.6 +/- 0.1) x 1014 L-circle dot mu(-1), where the total magnification mu(total) = 8.9 +/- 1.9, via a new lens model from the [C II] and continuum maps. Despite a HyLIRG luminosity, the FIR continuum shape resembles that of a local LIRG. We simultaneously fit all of the observed spectral line profiles, finding four components that correspond cleanly to discrete spatial structures identified in the maps. The two most redshifted spectral components occupy the nucleus of a massive galaxy, with a source-plane separation < 1 kpc. The reddest dominates the continuum map (demagnified L-FIR,L- (component) = (1.1 +/- 0.2) x10(13) L-circle dot) and excites strong water emission in both nuclear components via a powerful FIR radiation field from the intense star formation. A third star-forming component is most likely a region of a merging companion (Delta V similar to 500 kms(-1)) exhibiting generally similar gas properties. The bluest component originates from a spatially distinct region and photodissociation region analysis suggests that it is lower density, cooler, and forming stars less vigorously than the other components. Strikingly, it has very strong [N II] emission, which may suggest an ionized, molecular outflow. This comprehensive view of gas properties and morphology in HLS0918 previews the science possible for a large sample of high-redshift galaxies once ALMA attains full sensitivity.

We analyse new SCUBA-2 submillimeter and archival SPIRE far-infrared imaging of a z=1.62 cluster, Cl0218.3-0510, which lies in the UKIDSS/UDS field of the SCUBA-2 Cosmology Legacy Survey. Combining these tracers of obscured star formation activity with the extensive photometric and spectroscopic information available for this field, we identify 31 far-infrared/submillimeter-detected probable cluster members with bolometric luminosities >1e12 Lo and show that by virtue of their dust content and activity, these represent some of the reddest and brightest galaxies in this structure. We exploit Cycle-1 ALMA submillimeter continuum imaging which covers one of these sources to confirm the identification of a SCUBA-2-detected ultraluminous star-forming galaxy in this structure. Integrating the total star-formation activity in the central region of the structure, we estimate that it is an order of magnitude higher (in a mass-normalised sense) than clusters at z~0.5-1. However, we also find that the most active cluster members do not reside in the densest regions of the structure, which instead host a population of passive and massive, red galaxies. We suggest that while the passive and active populations have comparable near-infrared luminosities at z=1.6, M(H)~-23, the subsequent stronger fading of the more active galaxies means that they will evolve into passive systems at the present-day which are less luminous than the descendants of those galaxies which were already passive at z~1.6 (M(H)~-20.5 and M(H)~-21.5 respectively at z~0). We conclude that the massive galaxy population in the dense cores of present-day clusters were already in place at z=1.6 and that in Cl0218.3-0510 we are seeing continuing infall of less extreme, but still ultraluminous, star-forming galaxies onto a pre-existing structure.

We present the first photometric redshift distribution for a large sample of 870 mu m submillimeter galaxies (SMGs) with robust identifications based on observations with ALMA. In our analysis we consider 96 SMGs in the Extended Chandra Deep Field South, 77 of which have 4-19 band photometry. We model the SEDs for these 77 SMGs, deriving a median photometric redshift of z(phot) = 2.3 +/- 0.1. The remaining 19 SMGs have insufficient photometry to derive photometric redshifts, but a stacking analysis of Herschel observations confirms they are not spurious. Assuming that these SMGs have an absolute H-band magnitude distribution comparable to that of a complete sample of z similar to 1-2 SMGs, we demonstrate that they lie at slightly higher redshifts, raising the median redshift for SMGs to zphot = 2.5 +/- 0.2. Critically we show that the proportion of galaxies undergoing an SMG-like phase at z >= 3 is at most 35% +/- 5% of the total population. We derive a median stellar mass of M star = (8 +/- 1) x 10(10) M circle dot, although there are systematic uncertainties of up to 5 x for individual sources. Assuming that the star formation activity in SMGs has a timescale of similar to 100 Myr, we show that their descendants at z similar to 0 would have a space density and MH distribution that are in good agreement with those of local ellipticals. In addition, the inferred mass-weighted ages of the local ellipticals broadly agree with the look-back times of the SMG events. Taken together, these results are consistent with a simple model that identifies SMGs as events that form most of the stars seen in the majority of luminous elliptical galaxies at the present day.

The large gas and dust reservoirs of submillimeter galaxies (SMGs) could potentially provide ample fuel to trigger an active galactic nucleus (AGN), but previous studies of the AGN fraction in SMGs have been controversial largely due to the inhomogeneity and limited angular resolution of the available submillimeter surveys. Here we set improved constraints on the AGN fraction and X-ray properties of the SMGs with Atacama Large Millimeter/submillimeter Array (ALMA) and Chandra observations in the Extended Chandra Deep Field-South (E-CDF-S). This study is the first among similar works to have unambiguously identified the X-ray counterparts of SMGs; this is accomplished using the fully submillimeter-identified, statistically reliable SMG catalog with 99 SMGs from the ALMA LABOCA E-CDF-S Submillimeter Survey. We found 10 X-ray sources associated with SMGs (median redshift z = 2.3), of which eight were identified as AGNs using several techniques that enable cross-checking. The other two X-ray detected SMGs have levels of X-ray emission that can be plausibly explained by their star formation activity. Six of the eight SMG-AGNs are moderately/highly absorbed, with NH > 1023 cm−2. An analysis of the AGN fraction, taking into account the spatial variation of X-ray sensitivity, yields an AGN fraction of for AGNs with rest-frame 0.5–8 keV absorption-corrected luminosity ⩾7.8 × 1042 erg s−1; we provide estimated AGN fractions as a function of X-ray flux and luminosity. ALMA's high angular resolution also enables direct X-ray stacking at the precise positions of SMGs for the first time, and we found four potential SMG-AGNs in our stacking sample.

We analyse the SLEDs of 13CO and C18O for the J=1-0 up to J=7-6 transitions in the gravitationally lensed ultraluminous infrared galaxy SMMJ2135-0102 at z=2.3. This is the first detection of 13CO and C18O in a high-redshift star-forming galaxy. These data comprise observations of six transitions taken with PdBI and we combine these with 33GHz JVLA data and our previous 12CO and continuum emission information to better constrain the properties of the ISM within this system. We study both the velocity-integrated and kinematically decomposed properties of the galaxy and coupled with an LVG model we find that the star-forming regions in the system vary in their cold gas properties. We find strong C18O emission both in the velocity-integrated emission and in the two kinematic components at the periphery of the system, where the C18O line flux is equivalent to or higher than the 13CO. We derive an average velocity-integrated flux ratio of 13CO/C18O 1 suggesting a [13CO]/[C18O] abundance ratio at least 7x lower than that in the Milky Way. This may suggest enhanced C18O abundance, perhaps indicating star formation preferentially biased to high-mass stars. We estimate the relative contribution to the ISM heating from cosmic rays and UV of (30-3300)x10^(-25)erg/s and 45x10^(-25)erg/s per H2 molecule respectively and both are comparable to the total cooling rate of (0.8-20)x10^(-25)erg/s from the CO. However, our LVG models indicate high (>100K) temperatures and densities (>10^(3))cm^(-3) in the ISM which may suggest that cosmic rays play a more important role than UV heating in this system. If cosmic rays dominate the heating of the ISM, the increased temperature in the star forming regions may favour the formation of massive stars and so explain the enhanced C18O abundance. This is a potentially important result for a system which may evolve into a local elliptical galaxy.

We present new [C i](1-0) and (CO)-C-12(4-3) Plateau de Bure Interferometer observations of five sub-millimeter galaxies (SMGs) and combine these with all available [C i](1-0) literature detections in SMGs to probe the gas distribution within a sample of 14 systems. We explore the [C i](1-0) properties of the SMG population, particularly investigating the ratio of the [C i](1-0) luminosity to various (CO)-C-12 transition and far-infrared luminosities. We find that the SMGs with new observations extend the spread of L[Ci](1-0)/L-FIR to much higher values than found before, with our complete sample providing a good representation of the diverse z > 2 SMG population. We compare the line ratios to the outputs of photodissociation region (PDR) models to constrain the physical conditions in the interstellar medium (ISM) of the SMGs, finding an average density of << log (n/cm(-3))>> = 4.3 +/- 0.2 and an average radiation field (in terms of the local field value, G(0)) of << log (G(0))>> = 3.9 +/- 0.4. Overall, we find the SMGs are most comparable to local ultraluminous infrared galaxies (ULIRGs) in G(0) and n; however, a significant tail of 5 of the 14 SMGs are likely best compared to less compact, local starburst galaxies, providing new evidence that many SMGs have extended star formation distributions and are therefore not simply scaled up versions of local ULIRGs. We derive the ISM properties of a sample of quasars also finding that they have higher densities and radiation fields on average than the SMGs, consistent with the more extreme local ULIRGs, and reinforcing their interpretation as transition objects. We explore the limitations of using simple PDR models to understand [C i], which may be concomitant with the bulk H-2 mass rather than PDR distributed. We therefore also assess [C i] as a tracer of H-2, finding that for our sample SMGs, the H-2 masses derived from [C i] are often consistent with those determined from low excitation (CO)-C-12. We conclude that [C i] observations provide a useful tool to probe the bulk gas and gas processes occurring within merging SMGs, however more detailed, resolved observations are required to fully exploit [C i] as a diagnostic.

We investigate the multiwavelength properties of a sample of 450-μm-selected sources from the SCUBA-2 Cosmology Legacy Survey. 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 arcmin2 to a typical depth of σ450 = 1.5 mJy. Reliable cross-identifications 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 〈LIR〉 = 1012 ± 0.8 L⊙, 〈TD〉 = 42 ± 11 K and 〈βD〉 = 1.6 ± 0.5, respectively. The relationship between these SED parameters and the physical properties of galaxies is investigated, revealing correlations between TD and LIR and between βD and both stellar mass and effective radius. The connection between the star formation rate (SFR) and stellar mass is explored, with 24 per cent of 450-μm sources found to be ‘starbursts’, i.e. displaying anomalously high specific SFRs. However, both the number density and observed properties of these ‘starburst’ galaxies are found to be consistent with the population of normal star-forming galaxies.

We present an Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 0 survey of 126 submillimeter sources from the LABOCA ECDFS Submillimeter Survey (LESS). Our 870 mu m survey with ALMA (ALESS) has produced maps similar to 3x deeper and with a beam area similar to 200x smaller than the original LESS observations, doubling the current number of interferometrically-observed submillimeter sources. The high resolution of these maps allows us to resolve sources that were previously blended and accurately identify the origin of the submillimeter emission. We discuss the creation of the ALESS submillimeter galaxy (SMG) catalog, including the main sample of 99 SMGs and a supplementary sample of 32 SMGs. We find that at least 35% (possibly up to 50%) of the detected LABOCA sources have been resolved into multiple SMGs, and that the average number of SMGs per LESS source increases with LESS flux density. Using the (now precisely known) SMG positions, we empirically test the theoretical expectation for the uncertainty in the single-dish source positions. We also compare our catalog to the previously predicted radio/mid-infrared counterparts, finding that 45% of the ALESS SMGs were missed by this method. Our similar to 1 ''.6 resolution allows us to measure a size of similar to 9 kpc x 5 kpc for the rest-frame similar to 300 mu m emission region in one resolved SMG, implying a star formation rate surface density of 80 M-circle dot yr(-1) kpc(-2), and we constrain the emission regions in the remaining SMGs to be <10 kpc. As the first statistically reliable survey of SMGs, this will provide the basis for an unbiased multiwavelength study of SMG properties.