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The most intensively star-forming galaxies are extremely luminous at far-infrared (FIR) wavelengths, highly obscured at optical and ultraviolet wavelengths, and lie at |$z$| ≥ 1–3. We present a programme of FIR spectroscopic observations with the SPIRE FTS, as well as photometric observations with PACS, both on board Herschel, towards a sample of 45 gravitationally lensed, dusty starbursts across |$z$| ∼ 1–3.6. In total, we detected 27 individual lines down to |$3\, \sigma$|⁠, including nine [C  ii ] 158  |$\mu$| m lines with confirmed spectroscopic redshifts, five possible [C  ii ] lines consistent with their FIR photometric redshifts, and in some individual sources a few [O  iii ] 88  |$\mu$| m, [O  iii ] 52  |$\mu$| m, [O  i ] 145  |$\mu$| m, [O  i ] 63  |$\mu$| m, [N  ii ] 122  |$\mu$| m and OH 119  |$\mu$| m (in absorption) lines. To derive the typical physical properties of the gas in the sample, we stack all spectra weighted by their intrinsic luminosity and by their 500 |$\mu$| m flux densities, with the spectra scaled to a common redshift. In the stacked spectra, we detect emission lines of [C  ii ] 158  |$\mu$| m, [N  ii ] 122  |$\mu$| m, [O  iii ] 88  |$\mu$| m, [O  iii ] 52  |$\mu$| m, [O  i ] 63  |$\mu$| m and the absorption doublet of OH at 119  |$\mu$| m, at high fidelity. We find that the average electron densities traced by the [N  ii ] and [O  iii ] lines are higher than the average values in local star-forming galaxies and ULIRGs, using the same tracers. From the [N  ii ]/[C  ii ] and [O  i ]/[C  ii ] ratios, we find that the [C  ii ] emission is likely dominated by the photodominated regions (PDR), instead of by ionized gas or large-scale shocks. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We report the detection of the ground state rotational emission of ammonia, ortho-NH3 (JK  = 10 → 00) in a gravitationally lensed intrinsically hyperluminous star-bursting galaxy at z  = 2.6. The integrated line profile is consistent with other molecular and atomic emission lines which have resolved kinematics well modelled by a 5 kpc-diameter rotating disc. This implies that the gas responsible for NH3 emission is broadly tracing the global molecular reservoir, but likely distributed in pockets of high density (n ≳ 5 × 104 cm−3). With a luminosity of 2.8 × 106 L⊙, the NH3 emission represents 2.5 × 10−7 of the total infrared luminosity of the galaxy, comparable to the ratio observed in the Kleinmann–Low nebula in Orion and consistent with sites of massive star formation in the Milky Way. If |$L_{\rm NH_3}/L_{\rm IR}$| serves as a proxy for the 'mode' of star formation, this hints that the nature of star formation in extreme starbursts in the early Universe is similar to that of Galactic star-forming regions, with a large fraction of the cold interstellar medium in this state, plausibly driven by a storm of violent disc instabilities in the gas-dominated disc. This supports the 'full of Orions' picture of star formation in the most extreme galaxies seen close to the peak epoch of stellar mass assembly. [ABSTRACT FROM AUTHOR]

We report the results of a pilot study with the Expanded Very Large Array (EVLA) of CO emission from four submillimetre-selected galaxies at -2.5, each with an existing detection of CO , one of which comprises two distinct spatial components. Using the EVLA's most compact configuration, we detect strong, broad [medians: 990 km s full width at zero intensity; 540 km s full width at half-maximum (FWHM)] line emission from all of our targets - coincident in position and velocity with their emission. The median linewidth ratio, , suggests that the is more spatially extended than the emission, a situation confirmed by our maps which reveal velocity structure in several cases and typical sizes of 16 kpc FWHM. The median brightness temperature () ratio is , consistent with local galaxies with L, noting that our value may be biased high because of the based sample selection. Naively, this suggests gas masses roughly two times higher than estimates made using higher transitions of CO, with the discrepancy due entirely to the difference in assumed ratio. We also estimate molecular gas masses using the CO line and the observed global ratios, assuming standard underlying ratios for the non-star-forming and star-forming gas phases as well as a limiting star formation efficiency for the latter in all systems, i.e. without calling upon (). Using this new method, we find a median molecular gas mass of M, with a plausible range stretching up to three times higher. Even larger masses cannot be ruled out, but are not favoured by dynamical constraints: the median dynamical mass within kpc for our sample is M or 6 times more massive than UV-selected galaxies at this epoch. We examine the Schmidt-Kennicutt (S-K) relation for all the distant galaxy populations for which CO or data are available, finding small systematic differences between galaxy populations. These have previously been interpreted as evidence for different modes of star formation, but we argue that these differences are to be expected, given the still considerable uncertainties, certainly when considering the probable excitation biases due to the molecular lines used, and the possibility of sustained S-K offsets during the evolution of individual gas-rich systems. Finally, we discuss the morass of degeneracies surrounding molecular gas mass estimates, the possibilities for breaking them, and the future prospects for imaging and studying cold, quiescent molecular gas at high redshifts. [ABSTRACT FROM AUTHOR]

We investigate the correlation between far-infrared (FIR) and radio luminosities in distant galaxies, a lynchpin of modern astronomy. We use data from the Balloon-borne Large Aperture Submillimetre Telescope (BLAST), Spitzer, the Large Apex BOlometer CamerA (LABOCA), the Very Large Array and the Giant Metre-wave Radio Telescope (GMRT) in the Extended Chandra Deep Field South (ECDFS). For a catalogue of BLAST 250-μm-selected galaxies, we remeasure the 70–870-μm flux densities at the positions of their most likely 24-μm counterparts, which have a median [interquartile] redshift of 0.74 [0.25, 1.57]. From these, we determine the monochromatic flux density ratio, [ ]), and the bolometric equivalent, qIR. At , where our 250-μm filter probes rest-frame 160-μm emission, we find no evolution relative to for local galaxies. We also stack the FIR and submm images at the positions of 24-μm- and radio-selected galaxies. The difference between qIR seen for 250-μm- and radio-selected galaxies suggests that star formation provides most of the IR luminosity in ≲100-μJy radio galaxies, but rather less for those in the mJy regime. For the 24-μm sample, the radio spectral index is constant across , but qIR exhibits tentative evidence of a steady decline such that – significant evolution, spanning the epoch of galaxy formation, with major implications for techniques that rely on the FIR/radio correlation. We compare with model predictions and speculate that we may be seeing the increase in radio activity that gives rise to the radio background. [ABSTRACT FROM AUTHOR]

We have studied the μJy radio properties of K-selected galaxy populations detected in the Ultra-Deep Survey (UDS) portion of the United Kingdom Infrared Telescope (UKIRT) Deep Sky Survey using 610- and 1400-MHz images from the Very Large Array and the Giant Metre-wave Telescope. These deep radio mosaics, combined with the largest and deepest K-band image currently available, allow high signal-to-noise ratio (S/N) detections of many K-selected subpopulations, including sBzK and pBzK star-forming and passive galaxies. We find a strong correlation between the radio and K-band fluxes and a linear relationship between star formation rate (SFR) and K-band luminosity. We find no evidence, either from radio spectral indices or a comparison with submm-derived SFRs, that the full sample is strongly contaminated by active galactic nuclei (AGN) at these low flux densities, though this is very difficult to determine from this data set. The photometric redshift distributions for the BzK galaxies place 37 (29) per cent of pBzK (sBzK) galaxies at , implying that location on the BzK diagram alone is not sufficient to select samples at . The sBzK and pBzK galaxies have similar levels of radio flux density, SFR and specific SFR (SSFR – SFR per unit stellar mass) at , suggesting there is strong contamination of the pBzK sample by star-forming galaxies. At , the pBzK galaxies become difficult to detect in the radio stack, though the implied SFRs are still much higher than expected for passively evolving galaxies. It may be that their radio emission comes from low-luminosity AGN. Extremely red objects (EROs) straddle the passive and star-forming regions of the BzK diagram and also straddle the two groups in terms of their radio properties. We find that K-bright ERO samples are dominated by passive galaxies and faint ERO samples contain more star-forming galaxies. The star formation history (SFH) from stacking all K-band sources in the UDS agrees well with that derived for other wavebands and other radio surveys, at least out to . The radio-derived SFH then appears to fall more steeply than that measured at other wavelengths. The SSFR for K-selected sources rises strongly with redshift at all stellar masses, and shows a weak dependence on stellar mass. High- and low-mass galaxies show a similar decline in SSFR since . [ABSTRACT FROM AUTHOR]

Determining an accurate position for a submillimetre (submm) galaxy (SMG) is the crucial step that enables us to move from the basic properties of an SMG sample – source counts and 2D clustering – to an assessment of their detailed, multiwavelength properties, their contribution to the history of cosmic star formation and their links with present-day galaxy populations. In this paper, we identify robust radio and/or infrared (IR) counterparts, and hence accurate positions, for over two-thirds of the SCUBA HAlf-Degree Extragalactic Survey (SHADES) Source Catalogue, presenting optical, 24-μm and radio images of each SMG. Observed trends in identification rate have given no strong rationale for pruning the sample. Uncertainties in submm position are found to be consistent with theoretical expectations, with no evidence for significant additional sources of error. Employing the submm/radio redshift indicator, via a parametrization appropriate for radio-identified SMGs with spectroscopic redshifts, yields a median redshift of 2.8 for the radio-identified subset of SHADES, somewhat higher than the median spectroscopic redshift. We present a diagnostic colour–colour plot, exploiting Spitzer photometry, in which we identify regions commensurate with SMGs at very high redshift. Finally, we find that significantly more SMGs have multiple robust counterparts than would be expected by chance, indicative of physical associations. These multiple systems are most common amongst the brightest SMGs and are typically separated by 2–6 arcsec, at z∼ 2, consistent with early bursts seen in merger simulations. [ABSTRACT FROM AUTHOR]

Bolometer arrays on large antennas at high, dry sites have unveiled a dusty population of massive, luminous galaxies – submillimetre galaxies, or SMGs – which make a significant contribution to the star formation rate density at . The most crucial piece of information required to derive the history of obscured star formation is the redshift distribution of this galaxy population, N( z), which breaks degeneracies in the models and allows the mass and dynamics of the galaxies to be explored via high-resolution three-dimensional imaging in CO and by determining their level of clustering. Many SMGs are extremely faint, optically; some have no plausible counterparts, even in the infrared (IR), making the determination of an unbiased N( z) very difficult. The arrival of the Herschel Space Observatory and next-generation ground-based submm cameras will likely exacerbate this so-called redshift deadlock. Here, we report the first test of a new method for determining redshifts, based on the observed dependence of maser and IR luminosities. We have searched the dusty, lensed, hyperluminous quasar, APM 08279+5255, for the 1612-, 1665- and 1667-MHz hydroxyl lines as well as the 22-GHz water line. At , these are shifted to 329, 340 and 4538 MHz. Our relatively shallow test data reveal no convincing maser activity, but we set a meaningful constraint on the OH maser luminosity and we approach the expected thermal noise levels, meaning progress is possible. As an aside, we present deep new submm and radio imaging of this field. Using a simple shift-and-add technique, we uncover a new submm galaxy, conceivably at the redshift of APM 08279+5255. [ABSTRACT FROM AUTHOR]

We present new observations with the Atacama Large Millimeter/submillimeter Array of the 122 and 205 μm fine-structure line emission of singly ionized nitrogen in a strongly lensed starburst galaxy at z = 2.6. The 122/205 μm [N ii ] line ratio is sensitive to electron density, , in the ionized interstellar medium, and we use this to measure ne ≈ 300 cm−3, averaged across the galaxy. This is over an order of magnitude higher than the Milky Way average, comparable to localized Galactic star-forming regions. Combined with observations of the atomic carbon (C i) and carbon monoxide (CO J = 4–3) in the same system, we reveal the conditions in this intensely star-forming system. The majority of the molecular interstellar medium has been driven to high density, and the resultant conflagration of star formation produces a correspondingly dense ionized phase, presumably colocated with myriad H ii regions that litter the gas-rich disk. [ABSTRACT FROM AUTHOR]

We present the results of a survey of CO(1−0) emission in 14 infrared luminous dusty star-forming galaxies (DSFGs) at 2 < z < 4 with the NSF's Karl G. Jansky Very Large Array. All sources are detected in 12CO(1−0), with an angular resolution of ∼1″. Seven sources show extended and complex structure. We measure CO luminosities of (μ) L CO (1 − 0) ′ = 0.4 – 2.9 × 10 11 K km s−1 pc2, and molecular gas masses of (μ) M H 2 = 1.3 – 8.6 × 10 11 M ⊙, where (μ) is the magnification factor. The derived molecular gas depletion times of t dep = 40–460 Myr, cover the expected range of both normal star-forming galaxies and starbursts. Compared to the higher − J CO transitions previously observed for the same sources, we find CO temperature brightness ratios of r 32/10 = 0.4–1.4, r 43/10 = 0.4–1.7, and r 54/10 = 0.3–1.3. We find a wide range of CO spectral line energy distributions (SLEDs), in agreement with other high- z DSFGs, with the exception of three sources that are most comparable to Cloverleaf and APM08279+5255. Based on radiative transfer modeling of the CO SLEDs we determine densities of n H 2 = 0.3 − 8.5 × 10 3 cm−3 and temperatures of T K = 100–200 K. Lastly, four sources are detected in the continuum, three have radio emission consistent with their infrared-derived star formation rates, while HerBS-70E requires an additional synchrotron radiation component from an active galactic nucleus. Overall, we find that even though the sample is similarly luminous in the infrared, by tracing the CO(1−0) emission a diversity of galaxy and excitation properties are revealed, demonstrating the importance of CO(1−0) observations in combination to higher- J transitions. [ABSTRACT FROM AUTHOR]

We examine the far-infrared (FIR) properties of a sample of 5391 optically selected QSOs in the 0.5 < z < 2.65 redshift range down to log [ν L ν, 2500(erg s−1)] > 44.7, using SPIRE data from Herschel -ATLAS. We split the sample in a grid of 74 luminosity–redshift bins and compute the average optical–IR spectral energy distribution (SED) in each bin. By normalizing an intrinsic active galactic nucleus (AGN) template to the AGN optical power (at 5100 Å), we decompose the total IR emission (L IR; 8–1000 µm) into an AGN (L IR, AGN) and star-forming component (L IR, SF). We find that the AGN contribution to L IR increases as a function of AGN power, manifesting as a reduction of the 'FIR bump' in the average QSO SEDs. We note that L IR, SF does not correlate with AGN power; the mean star formation rates (SFRs) of AGN host galaxies are a function of redshift only and they range from ∼6 M⊙ yr−1 at z ∼ 0 to a plateau of ≲ 200 M⊙ yr−1 at z ∼ 2.6. Our results indicate that the accuracy of FIR emission as a proxy for SFR decreases with increasing AGN luminosity. We show that, at any given redshift, observed trends between IR luminosity (whether monochromatic or total) and AGN power (in the optical or X-rays) can be explained by a simple model which is the sum of two components: (i) the IR emission from star formation, uncorrelated with AGN power and (ii) the IR emission from AGN, directly proportional to AGN power in the optical or X-rays. [ABSTRACT FROM AUTHOR]

ABSTRACT The Astronomical Thermal Emission Camera (AzTEC) 1.1 mm survey of the two SCUBA HAlf Degree Extragalactic Survey (SHADES) fields is the largest (0.7 deg2) blank-field millimetre-wavelength (mm-wavelength) survey undertaken to date at a resolution of ≃18 arcsec and a depth of ≃1 mJy. We have used the deep optical to radio multiwavelength data in the SHADES Lockman Hole East and SXDF/UDS fields to obtain galaxy identifications for ≃64 per cent (≃80 per cent including tentative identifications) of the 148 AzTEC-SHADES 1.1 mm sources reported by Austermann et al., exploiting deep radio and 24 μm data complemented by methods based on 8 μm flux density and red optical-infrared ( i − K) colour. This unusually high identification rate can be attributed to the relatively bright mm-wavelength flux density threshold, combined with the relatively deep supporting multifrequency data now available in these two well-studied fields. We have further exploited the optical-mid-infrared-radio data to derive an ≃60 per cent (≃75 per cent including tentative identifications) complete redshift distribution for the AzTEC-SHADES sources, yielding a median redshift of z ≃ 2.2, with a high-redshift tail extending to at least z ≃ 4. Despite the larger area probed by the AzTEC survey relative to the original SCUBA-SHADES imaging, the redshift distribution of the AzTEC sources is consistent with that displayed by the SCUBA sources, and reinforces tentative evidence that the redshift distribution of mm/submm sources in the Lockman Hole field is significantly different from that found in the SXDF/UDS field. Comparison with simulated surveys of similar scale extracted from semi-analytic models based on the Millennium simulation indicates that this is as expected if the mm/submm sources are massive ( M > 1011 M⊙) star-forming galaxies tracing large-scale structures over scales of 10-20 Mpc. This confirms the importance of surveys covering several deg2 (as now underway with SCUBA2) to obtain representative samples of bright (sub)mm-selected galaxies. This work provides a foundation for the further exploitation of the Spitzer and Herschel data in the SHADES fields in the study of the stellar masses and specific star formation rates of the most active star-forming galaxies in cosmic history. [ABSTRACT FROM AUTHOR]

Nuclear starbursts may contribute to the obscuration of active galactic nuclei (AGNs). The predicted star formation rates (SFRs) are modest, and, for the obscured AGNs that form the X-ray background at z < 1, the associated faint radio emission lies just beyond the sensitivity limits of the deepest surveys. Here, we search for this level of star formation by studying a sample of 359 X-ray-selected AGNs at z < 1 from the Cosmic Evolution Survey field that are not detected by current radio surveys. The AGNs are separated into bins based on redshift, X-ray luminosity, obscuration, and mid-infrared characteristics. An estimate of the AGN contribution to the radio flux density is subtracted from each radio image, and the images are then stacked to uncover any residual faint radio flux density. All of the bins containing 24 µm detected AGNs are detected with a signal-to-noise >3σ in the stacked radio images. In contrast, AGNs not detected at 24 µm are not detected in the resulting stacked radio images. This result provides strong evidence that the stacked radio signals are likely associated with star formation. The estimated SFRs derived from the radio stacks range from 3 M⊙ yr-1 to 29 M⊙ yr-1. Although it is not possible to associate the radio emission with a specific region of the host galaxies, these results are consistent with the predictions of nuclear starburst disks in AGN host galaxies. [ABSTRACT FROM AUTHOR]

ABSTRACT We present continent-scale very-long-baseline interferometry (VLBI) - obtained with the European VLBI Network (EVN) at a wavelength of 18 cm - of six distant, luminous submillimetre-selected galaxies (SMGs). Our images have a synthesized beamwidth of ≈30 mas FWHM - three orders of magnitude smaller in area than the highest resolution Very Large Array (VLA) imaging at this frequency - and are capable of separating radio emission from ultra-compact radio cores (associated with active super-massive black holes - SMBHs) from that due to starburst activity. Despite targeting compact sources - as judged by earlier observations with the VLA and MERLIN - we identify ultra-compact cores in only two of our targets. This suggests that the radio emission from SMGs is produced primarily on larger scales than those probed by the EVN, and therefore is generated by star formation rather than an active galactic nucleus (AGN) - a result consistent with other methods used to identify the presence of SMBHs in these systems. [ABSTRACT FROM AUTHOR]

We present observations of a giant Lyα blob (LAB) in the SSA22 protocluster at z = 3.1, SSA22-LAB1, taken with the Atacama Large Millimeter/submillimeter Array. Dust continuum, along with [C ii ] 158 μm and CO(4–3) line emission have been detected in LAB1, showing complex morphology and kinematics across a ∼100 kpc central region. Seven galaxies at z = 3.0987–3.1016 in the surroundings are identified in [C ii ] and dust continuum emission, with two of them potential companions or tidal structures associated with the most massive galaxies. Spatially resolved [C ii ] and infrared luminosity ratios for the widely distributed media (L[Cɪɪ]/LIR ≈ 10−2−10−3) suggest that the observed extended interstellar media are likely to have originated from star formation activity and the contribution from shocked gas is probably not dominant. LAB1 is found to harbor a total molecular gas mass Mmol = (8.7 ± 2.0) × 1010M⊙, concentrated in the core region of the Lyα-emitting area. While (primarily obscured) star formation activity in the LAB1 core is one of the most plausible power sources for the Lyα emission, multiple major mergers found in the core may also play a role in making LAB1 exceptionally bright and extended in Lyα as a result of cooling radiation induced by gravitational interactions. [ABSTRACT FROM AUTHOR]

We present Large Millimeter Telescope (LMT)/AzTEC 1.1 mm observations of ∼100 luminous high-redshift dusty star-forming galaxy candidates from the |$\sim 600\,$|  sq.deg Herschel -ATLAS survey, selected on the basis of their SPIRE red far-infrared colours and with |$S_{500\, \mu \rm m}=35-80$| mJy. With an effective |$\theta _{\rm FWHM}\approx 9.5\,$| arcsec angular resolution, our observations reveal that at least 9 per cent of the targets break into multiple systems with signal-to-noise ratio ≥4 members. The fraction of multiple systems increases to ∼23 per cent (or more) if some non-detected targets are considered multiples, as suggested by the data. Combining the new AzTEC and deblended Herschel photometry, we derive photometric redshifts, infrared luminosities, and star formation rates. While the median redshifts of the multiple and single systems are similar (z med ≈ 3.6), the redshift distribution of the latter is skewed towards higher redshifts. Of the AzTEC sources, ∼85 per cent lie at z phot > 3 while ∼33 per cent are at z phot > 4. This corresponds to a lower limit on the space density of ultrared sources at 4 < z < 6 of |$\sim 3\times 10^{-7}\, \textrm {Mpc}^{-3}$| with a contribution to the obscured star formation of |$\gtrsim 8\times 10^{-4}\, \textrm {M}_\odot \, \textrm {yr}^{-1} \, \textrm {Mpc}^{-3}$|⁠. Some of the multiple systems have members with photometric redshifts consistent among them suggesting possible physical associations. Given their angular separations, these systems are most likely galaxy over-densities and/or early-stage pre-coalescence mergers. Finally, we present 3 mm LMT/RSR spectroscopic redshifts of six red- Herschel galaxies at z spec = 3.85−6.03, two of them (at z ∼ 4.7) representing new redshift confirmations. Here, we release the AzTEC and deblended Herschel photometry as well as catalogues of the most promising interacting systems and z > 4 galaxies. [ABSTRACT FROM AUTHOR]

We present an analysis of the spatial clustering of a large sample of high-resolution, interferometically identified, submillimetre galaxies (SMGs). We measure the projected cross-correlation function of ∼350 SMGs in the UKIDSS Ultra Deep-Survey Field across a redshift range of z = 1.5–3 utilizing a method that incorporates the uncertainties in the redshift measurements for both the SMGs and cross-correlated galaxies through sampling their full probability distribution functions. By measuring the absolute linear bias of the SMGs, we derive halo masses of |$\log _{10}(M_{\rm halo}[{h^{-1}\, \rm M_{\odot }}])$| ∼ 12.8 with no evidence of evolution in the halo masses with redshift, contrary to some previous work. From considering models of halo mass growth rates, we predict that the SMGs will reside in haloes of mass |$\log _{10}(M_{\rm halo}[{h^{-1}\, \rm M_{\odot }}])$| ∼ 13.2 at z = 0, consistent with the expectation that the majority of z = 1.5–3 SMGs will evolve into present-day spheroidal galaxies. Finally, comparing to models of stellar-to-halo mass ratios, we show that SMGs may correspond to systems that are maximally efficient at converting their gas reservoirs into stars. We compare them to a simple model for gas cooling in haloes that suggests that the unique properties of the SMG population, including their high levels of star formation and their redshift distribution, are a result of the SMGs being the most massive galaxies that are still able to accrete cool gas from their surrounding intragalactic medium. [ABSTRACT FROM AUTHOR]

We present new empirical constraints on the evolution of , the cosmological mass density of molecular hydrogen, back to z ≈ 2.5. We employ a statistical approach measuring the average observed 850 μm flux density of near-infrared selected galaxies as a function of redshift. The redshift range considered corresponds to a span where the 850 μm band probes the Rayleigh–Jeans tail of thermal dust emission in the rest frame, and can therefore be used as an estimate of the mass of the interstellar medium. Our sample comprises of ≈150,000 galaxies in the UK InfraRed Telescope Infrared Deep Sky Survey Ultra-Deep Survey field with near-infrared magnitudes KAB ≤ 25 mag and photometric redshifts with corresponding probability distribution functions derived from deep 12-band photometry. With a sample approximately 2 orders of magnitude larger than in previous works we significantly reduce statistical uncertainties on to z ≈ 2.5. Our measurements are in broad agreement with recent direct estimates from blank field molecular gas surveys, finding that the epoch of molecular gas coincides with the peak epoch of star formation with at z ≈ 2. We demonstrate that can be broadly modeled by inverting the star formation rate (SFR) density with a fixed or weakly evolving star formation efficiency. This "constant efficiency" model shows a similar evolution to our statistically derived , indicating that the dominant factor driving the peak star formation history at z ≈ 2 is a larger supply of molecular gas in galaxies rather than a significant evolution of the SFR efficiency within individual galaxies. [ABSTRACT FROM AUTHOR]

We analyse a robust sample of 30 near-infrared-faint (K AB > 25.3, 5σ) submillimetre galaxies (SMGs) selected from a 0.96 deg2 field to investigate their properties and the cause of their faintness in optical/near-infrared wavebands. Our analysis exploits precise identifications based on Atacama Large Millimeter Array (ALMA) 870- μ m continuum imaging, combined with very deep near-infrared imaging from the UKIDSS Ultra Deep Survey. We estimate that SMGs with K AB > 25.3 mag represent 15 ± 2 per cent of the total population brighter than S 870 = 3.6 mJy, with a potential surface density of ∼450 deg−2 above S 870 ≥ 1 mJy. As such, they pose a source of contamination in surveys for both high-redshift 'quiescent' galaxies and very high redshift Lyman-break galaxies. We show that these K -faint SMGs represent the tail of the broader submillimetre population, with comparable dust and stellar masses to K AB ≤ 25.3 mag SMGs, but lying at significantly higher redshifts (z = 3.44 ± 0.06 versus z = 2.36 ± 0.11) and having higher dust attenuation (AV = 5.2 ± 0.3 versus AV = 2.9 ± 0.1). We investigate the origin of the strong dust attenuation and find indications that these K -faint galaxies have smaller dust continuum sizes than the K AB ≤ 25.3 mag galaxies, as measured by ALMA, which suggests their high attenuation is related to their compact sizes. We identify a correlation of dust attenuation with star formation rate surface density (ΣSFR), with the K -faint SMGs representing the higher ΣSFR and highest AV galaxies. The concentrated, intense star formation activity in these systems is likely to be associated with the formation of spheroids in compact galaxies at high redshifts, but as a result of their high obscuration these galaxies are completely missed in ultraviolet, optical, and even near-infrared surveys. [ABSTRACT FROM AUTHOR]

We present Atacama Large Millimeter/Submillimeter Array (ALMA) continuum observations of a sample of nine star-forming galaxies at redshifts 1.47 and 2.23 selected from the High- z Emission Line Survey (HiZELS). Four galaxies in our sample are detected at high significance by ALMA at a resolution of 0 |${_{.}^{\prime\prime}}$| 25 at rest-frame 355 μm. Together with the previously observed H α emission, from adaptive optics-assisted integral-field-unit spectroscopy (∼0 |${_{.}^{\prime\prime}}$| 15 resolution), and F606W and F140W imaging from the Hubble Space Telescope (∼0 |${_{.}^{\prime\prime}}$| 2 resolution), we study the star formation activity, stellar and dust mass in these high-redshift galaxies at ∼kpc-scale resolution. We find that ALMA detection rates are higher for more massive galaxies (M * > 1010.5 M⊙) and higher [N  ii ]/H α ratios (>0.25, a proxy for gas-phase metallicity). The dust extends out to a radius of 8 kpc, with a smooth structure, even for those galaxies presenting clumpy H α morphologies. The half-light radii (R dust) derived for the detected galaxies are of the order ∼4.5 kpc, more than twice the size of submillimetre-selected galaxies at a similar redshift. Our global star formation rate estimates – from far-infrared and extinction-corrected H α luminosities – are in good agreement. However, the different morphologies of the different phases of the interstellar medium suggest complex extinction properties of the high-redshift normal galaxies. [ABSTRACT FROM AUTHOR]

We present Atacama Large Millimeter/sub-millimeter Array (ALMA) observations towards 27 low-redshift (0.02 < z < 0.2) star-forming galaxies taken from the Valparaíso ALMA/APEX Line Emission Survey. We perform stacking analyses of the 12CO(1–0), 13CO(1–0), and C18O(1–0) emission lines to explore the L ′ [12CO(1–0)]/ L ′ [13CO(1–0)] [hereafter L ′ (12CO)/ L ′ (13CO)] and L ′ [13CO(1–0)]/ L ′ [C18O(1–0)] [hereafter L ′ (13CO)/ L ′ (C18O)] line luminosity ratio dependence as a function of different global galaxy parameters related to the star formation activity. The sample has far-IR luminosities of |$10^{10.1\!-\!11.9}\,$|  L⊙ and stellar masses of 109.8–10.9 M⊙ corresponding to typical star-forming and starburst galaxies at these redshifts. On average, we find an L ′ (12CO)/ L ′ (13CO) line luminosity ratio value of 16.1 ± 2.5. Galaxies with pieces of evidence of possible merging activity tend to show higher L ′ (12CO)/ L ′ (13CO) ratios by a factor of 2, while variations of this order are also found in galaxy samples with higher star formation rates (SFRs) or star formation efficiencies (SFEs). We also find an average L ′ (13CO)/ L ′ (C18O) line luminosity ratio of 2.5 ± 0.6, which is in good agreement with those previously reported for starburst galaxies. We find that galaxy samples with high L IR, SFR, and SFE show low L ′ (13CO)/ L ′ (C18O) line luminosity ratios with high L ′ (12CO)/ L ′ (13CO) line luminosity ratios, suggesting that these trends are produced by selective enrichment of massive stars in young starbursts. [ABSTRACT FROM AUTHOR]

Measurements of the cosmic far-infrared background (CIB) indicate that emission from many extragalactic phenomena, including star formation and black hole accretion, in the Universe can be obscured by dust. Resolving the CIB to study the population of galaxies in which this activity takes place is a major goal of submillimetre astronomy. Here, we present interferometric 650 μm submillimetre number counts. Using the Band 8 data from the ALMACAL survey, we have analysed 81 ALMA calibrator fields together covering a total area of 5.5 arcmin2. The typical central rms in these fields is ∼100 μJy beam−1 with the deepest maps reaching σ = 47 μJy beam−1 at sub-arcsec resolution. Multiwavelength coverage from ALMACAL allows us to exclude contamination from jets associated with the calibrators. However, residual contamination by jets and lensing remain a possibility. Using a signal-to-noise threshold of 4.5σ, we find 21 dusty, star-forming galaxies with 650 μm flux densities of ≥0.7mJy. At the detection limit we resolve ≃100 per cent of the CIB at 650 μm, a significant improvement compared to low-resolution studies at similar wavelength. We have therefore identified all the sources contributing to the EBL at 650 μm and predict that the contribution from objects with flux 0.7 mJy will be small. [ABSTRACT FROM AUTHOR]

We analyse 870  |$\mu$| m Atacama Large Millimetre Array (ALMA) dust continuum detections of 41 canonically selected |$z$| ≃ 3 Lyman-break galaxies (LBGs), as well as 209 ALMA-undetected LBGs, in follow-up of SCUBA-2 mapping of the UKIDSS Ultra Deep Survey (UDS) field. We find that our ALMA-bright LBGs lie significantly off the local IRX-beta relation and have relatively bluer rest-frame UV slopes (as parametrized by β), given their high values of the 'infrared excess' (IRX ≡ L IR/ L UV), relative to the average 'local' IRX-β relation. We attribute this finding in part to the young ages of the underlying stellar populations but we find that the main reason behind the unusually blue UV slopes are the relatively shallow slopes of the corresponding dust attenuation curves. We show that, when stellar masses, M *, are being established via SED fitting, it is absolutely crucial to allow the attenuation curves to vary (rather than fixing it on Calzetti-like law), where we find that the inappropriate curves may underestimate the resulting stellar masses by a factor of ≃2–3× on average. In addition, we find these LBGs to have relatively high specific star-formation rates (sSFRs), dominated by the dust component, as quantified via the fraction of obscured star formation |$(f_{\rm obs}\equiv {\rm SFR_{\rm IR}/{\rm SFR}_{\rm UV+IR}})$|⁠. We conclude that the ALMA-bright LBGs are, by selection, massive galaxies undergoing a burst of a star formation (large sSFRs, driven, for example, by secular or merger processes), with a likely geometrical disconnection of the dust and stars, responsible for producing shallow dust attenuation curves. [ABSTRACT FROM AUTHOR]

We are just starting to understand the physical processes driving the dramatic change in cosmic star formation rate between z ∼ 2 and the present day. A quantity directly linked to star formation is the molecular gas density, which should be measured through independent methods to explore variations due to cosmic variance and systematic uncertainties. We use intervening CO absorption lines in the spectra of mm-bright background sources to provide a census of the molecular gas mass density of the Universe. The data used in this work are taken from ALMACAL, a wide and deep survey utilizing the ALMA calibrator archive. While we report multiple Galactic absorption lines and one intrinsic absorber, no extragalactic intervening molecular absorbers are detected. However, due to the large redshift path surveyed (Δ z  = 182), we provide constraints on the molecular column density distribution function beyond z ∼ 0. In addition, we probe column densities of N (H2) > 1016 atoms cm−2, 5 orders of magnitude lower than in previous studies. We use the cosmological hydrodynamical simulation IllustrisTNG to show that our upper limits of |$\rho ({\rm H}_2)\lesssim 10^{8.3}\, \text{M}_{\odot }\, \text{Mpc}^{-3}$| at 0 < z ≤ 1.7 already provide new constraints on current theoretical predictions of the cold molecular phase of the gas. These results are in agreement with recent CO emission-line surveys and are complementary to those studies. The combined constraints indicate that the present decrease of the cosmic star formation rate history is consistent with an increasing depletion of molecular gas in galaxies compared to z ∼ 2. [ABSTRACT FROM AUTHOR]

We identify multi-wavelength counterparts to 1147 submillimeter sources from the S2COSMOS SCUBA-2 survey of the COSMOS field by employing a recently developed radio+machine-learning method trained on a large sample of Atacama Large Millimeter/submillimeter Array (ALMA)–identified submillimeter galaxies (SMGs), including 260 SMGs identified in the AS2COSMOS pilot survey. In total, we identify 1222 optical/near-infrared (NIR)/radio counterparts to the 897 S2COSMOS submillimeter sources with S850 > 1.6 mJy, yielding an overall identification rate of (78 ± 9)%. We find that (22 ± 5)% of S2COSMOS sources have multiple identified counterparts. We estimate that roughly 27% of these multiple counterparts within the same SCUBA-2 error circles very likely arise from physically associated galaxies rather than line-of-sight projections by chance. The photometric redshift of our radio+machine-learning-identified SMGs ranges from z = 0.2 to 5.7 and peaks at z = 2.3 ± 0.1. The AGN fraction of our sample is (19 ± 4)%, which is consistent with that of ALMA SMGs in the literature. Comparing with radio/NIR-detected field galaxy population in the COSMOS field, our radio+machine-learning-identified counterparts of SMGs have the highest star formation rates and stellar masses. These characteristics suggest that our identified counterparts of S2COSMOS sources are a representative sample of SMGs at z ≲ 3. We employ our machine-learning technique to the whole COSMOS field and identified 6877 potential SMGs, most of which are expected to have submillimeter emission fainter than the confusion limit of our S2COSMOS surveys (mJy). We study the clustering properties of SMGs based on this statistically large sample, finding that they reside in high-mass dark matter halos ((1.2 ± 0.3) × 1013h−1), which suggests that SMGs may be the progenitors of massive ellipticals we see in the local universe. [ABSTRACT FROM AUTHOR]

Cosmological simulations predict that the Universe contains a network of intergalactic gas filaments, within which galaxies form and evolve. However, the faintness of any emission from these filaments has limited tests of this prediction. We report the detection of rest-frame ultraviolet Lyman-a radiation from multiple filaments extending more than one megaparsec between galaxies within the SSA22 protocluster at a redshift of 3.1. Intense star formation and supermassive black-hole activity is occurring within the galaxies embedded in these structures, which are the likely sources of the elevated ionizing radiation powering the observed Lyman-α emission. Our observations map the gas in filamentary structures of the type thought to fuel the growth of galaxies and black holes in massive protoclusters. [ABSTRACT FROM AUTHOR]

We present James Clerk Maxwell Telescope Submillimetre Common-User Bolometer Array 2 (SCUBA-2) 850 and 450 |$\mu$| m observations (σ850 ∼ 0.5 mJy, σ450 ∼ 5 mJy) of the HS1549+19 and HS1700+64 survey fields containing two of the largest known galaxy overdensities at z  = 2.85 and 2.30, respectively. We detect 56 sub-millimetre galaxies (SMGs) with SNR > 4 over ∼50 arcmin2 at 850 |$\mu$| m with flux densities of 3–17 mJy. The number counts indicate overdensities in the 3-arcmin diameter core region (∼1.5 Mpc at z  = 2.5) of |$6^{+4}_{-2}\times$| (HS1549) and |$4^{+6}_{-2}\times$| (HS1700) compared to blank field surveys. Within these core regions, we spectroscopically confirm that approximately one-third of the SMGs lie at the protocluster redshifts for both HS1549 and HS1700. We use statistical identifications of other SMGs in the wider fields to constrain an additional four candidate protocluster members in each system. We combine multiwavelength estimates of the star-formation rates (SFRs) from Lyman-break dropout- and narrow-band-selected galaxies, and the SCUBA-2 SMGs, to estimate total SFRs of 12 500 ± 2800 M⊙ yr−1 (4900 ± 1200 M⊙ yr−1) in HS1549 (HS1700), and SFR densities (SFRDs) within the central 1.5-Mpc diameter of each protocluster to be 3000 ± 900 M⊙ yr−1 Mpc−3 (1300 ± 400 M⊙ yr−1 Mpc−3) in the HS1549 (HS1700) protocluster, ∼104 × larger than the global SFRDs found at their respective epochs, due to the concentration of star-forming galaxies in the small volume of the dense cluster cores. Our results suggest centrally concentrated starbursts within protoclusters may be a relatively common scenario for the build-up of mass in rich clusters assembling at z ≳ 2. [ABSTRACT FROM AUTHOR]

The Herschel Space Observatory has revealed a very different galaxyscape from that shown by optical surveys which presents a challenge for galaxy-evolution models. The Herschel surveys reveal (1) that there was rapid galaxy evolution in the very recent past and (2) that galaxies lie on a single Galaxy Sequence (GS) rather than a star-forming 'main sequence' and a separate region of 'passive' or 'red-and-dead' galaxies. The form of the GS is now clearer because far-infrared surveys such as the Herschel ATLAS pick up a population of optically red starforming galaxies that would have been classified as passive using most optical criteria. The space-density of this population is at least as high as the traditional star-forming population. By stacking spectra of H-ATLAS galaxies over the redshift range 0.001 < z < 0.4, we show that the galaxies responsible for the rapid low-redshift evolution have high stellar masses, high star-formation rates but, even several billion years in the past, old stellar populations - they are thus likely to be relatively recent ancestors of early-type galaxies in the Universe today. The form of the GS is inconsistent with rapid quenching models and neither the analytic bathtub model nor the hydrodynamical EAGLE simulation can reproduce the rapid cosmic evolution. We propose a new gentler model of galaxy evolution that can explain the new Herschel results and other key properties of the galaxy population. [ABSTRACT FROM AUTHOR]

We present an extragalactic survey using observations from the Atacama Large Millimeter/ submillimeter Array (ALMA) to characterize galaxy populations up to z = 0.35: the ValparaÍso ALMA Line Emission Survey (VALES). We use ALMA Band-3 CO(1-0) observations to study themolecular gas content in a sample of 67 dusty normal star-forming galaxies selected from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). We have spectrally detected 49 galaxies at >5σ significance and 12 others are seen at low significance in stacked spectra. CO luminosities are in the range of (0.03-1.31) × 1010 K km s-1 pc2, equivalent to log(Mgas/M☉) = 8.9-10.9 assuming an αCO = 4.6 (K km s-1 pc2)-1, which perfectly complements the parameter space previously explored with local and high-z normal galaxies. We compute the optical to CO size ratio for 21 galaxies resolved by ALMA at ~3.5 arcsec resolution (6.5 kpc), finding that the molecular gas is on average ~0.6 times more compact than the stellar component. We obtain a global Schmidt-Kennicutt relation, given by log[∑SFR/(M☉ yr-1 kpc-2)] = (1.26 ± 0.02) × log[∑MH2/(M☉ pc-2)] - (3.6 ± 0.2). We find a significant fraction of galaxies lying at 'intermediate efficiencies' between a longstanding mode of star formation activity and a starburst, specially at LIR = 1011-12 L☉. Combining our observations with data taken from the literature, we propose that star formation efficiencies can be parametrized by log [SFR/MH2 ] = 0.19 × (log LIR - 11.45) - 8.26 - 0.41 × arctan[-4.84 (logLIR - 11.45)]. Within the redshift range we explore (z < 0.35), we identify a rapid increase of the gas content as a function of redshift. [ABSTRACT FROM AUTHOR]

We use state-of-the-art chemical models to track the cosmic evolution of the CNO isotopes in the interstellar medium of galaxies, yielding powerful constraints on their stellar initial mass function (IMF). We re-assess the relative roles of massive stars, asymptotic giant branch (AGB) stars and novae in the production of rare isotopes such as 13C, 15N, 17O and 18O, along with 12C, 14N and 16O. The CNO isotope yields of super-AGB stars, novae and fast-rotating massive stars are included. Having reproduced the available isotope enrichment data in the solar neighbourhood, and across the Galaxy, and having assessed the sensitivity of our models to the remaining uncertainties, e.g. nova yields and star formation history, we show that we can meaningfully constrain the stellar IMF in galaxies using C, O and N isotope abundance ratios. In starburst galaxies, where data for multiple isotopologue lines are available, we find compelling new evidence for a top-heavy stellar IMF, with profound implications for their star formation rates and efficiencies, perhaps also their stellar masses. Neither chemical fractionation nor selective photodissociation can significantly perturb globally averaged isotopologue abundance ratios away from the corresponding isotope ones, as both these processes will typically affect only small mass fractions of molecular clouds in galaxies. Thus, the Atacama LargeMillimeter Array now stands ready to probe the stellar IMF, and even the ages of specific starburst events in star-forming galaxies across cosmic time unaffected by the dust obscuration effects that plague optical/near-infrared studies. [ABSTRACT FROM AUTHOR]

We present the calibration between the dust continuum luminosity and interstellar gas content obtained from the Valparaíso ALMA Line Emission Survey (VALES) sample of 67 mainsequence star-forming galaxies at 0.02 < z < 0.35. We use CO(1-0) observations from the Atacama Large Millimetre/submillimetre Array to trace the molecular gas mass, MH2 , and estimate the rest-frame monochromatic luminosity at 850 μm, Lν 850 , by extrapolating the dust continuum from MAGPHYS modelling of the far-ultraviolet to submillimetre spectral energy distribution sampled by the Galaxy And Mass Assembly survey. Adopting αCO = 6.5 (K km s-1 pc2)-1, the average ratio of Lν 850 /MH2 = (6.4 ± 1.4)× 1019 erg s-1 Hz-1 M-1☉, in excellent agreement with literature values. We obtain a linear fit of log10(MH2/M☉) = (0.92 ± 0.02) log10(Lν 850/erg s-1 Hz-1) - (17.31 ± 0.59).We provide relations between Lν 850 , MH2 and MISM when combining the VALES and literature samples, and adopting a Galactic αCO value. [ABSTRACT FROM AUTHOR]

We use new Band 3 CO(1-0) observations taken with the Atacama Large Millimeter/submillimeter Array (ALMA) to study the physical conditions in the interstellar gas of a sample of 27 dusty main-sequence star-forming galaxies at 0:03 < z < 0:2 present in the Valparaíso ALMA Line Emission Survey (VALES). The sample is drawn from far-IR bright galaxies over ~160 deg2 in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS), which is covered by high-quality ancillary data including Herschel [Cπ] 158 μm spectroscopy and far-infrared (FIR) photometry. The [Cπ] and CO(1-0) lines are both detected at >5σ in 26 sources. We find an average [Cπ] to CO(1-0) luminosity ratio of 3500 ± 1200 for our sample that is consistent with previous studies. Using the [Cπ], CO(1-0) and FIR measurements as diagnostics of the physical conditions of the interstellar medium, we compare these observations to the predictions of a photodissociation region (PDR) model to determine the gas density, surface temperature, pressure, and the strength of the incident far-ultraviolet (FUV) radiation field, G0, normalised to the Habing Field. The majority of our sample exhibit hydrogen densities of 4 < log n=cm³ < 5:5 and experience an incident FUV radiation field with strengths of 2 < logG0 < 3 when adopting standard adjustments. A comparison to galaxy samples at different redshifts indicates that the average strength of the FUV radiation field appears constant up to redshift z ~ 6:4, yet the neutral gas density increases as a function of redshift by a factor of ~100 from z = 0 to z = 0:2 that persists regardless of various adjustments to our observable quantities. Whilst this evolution could provide an explanation for the observed evolution of the star formation rate density with cosmic time, the result most likely arises from a combination of observational biases when using different suites of emission lines as diagnostic tracers of PDR gas. [ABSTRACT FROM AUTHOR]

We present the first results from our ongoing Australia Telescope Compact Array survey of 12CO(1-0) in Atacama Large Millimeter Array (ALMA)-identified submillimetre galaxies (SMGs) in the Extended Chandra Deep Field South. Strong detections of 12CO (1-0) emission from two SMGs, ALESS 122.1 (z = 2.0232) and ALESS 67.1 (z = 2.1230), were obtained. We estimate gas masses of Mgas ~ 1.3 x 1011 Mʘ and Mgas ~ 1.0 x 1011 Mʘ for ALESS 122.1 and ALESS 67.1, respectively, adopting αCO = 1.0. Dynamical mass estimates from the kinematics of the 12CO(1-0) line yields Mdyn sin² i = (2.1 ± 1.1) x 1011 Mʘ and (3.2 ± 0.9) x 1011 Mʘ for ALESS 122.1 and ALESS 67.1, respectively. This is consistent with the total baryonic mass estimates of these two systems. We examine star formation efficiency, using the LFIR versus L'CO(1-0) relation for samples of local ultraluminous infrared galaxies (ULIRGs) and Luminous Infrared Galaxies (LIRGs), and more distant star-forming galaxies, with 12CO(1-0) detections. We find some evidence of a shallower slope for ULIRGs and SMGs compared to less luminous systems, but a larger sample is required for definite conclusions. We determine gas-to-dust ratios of 170 ± 30 and 140 ± 30 for ALESS 122.1 and ALESS 67.1, respectively, showing that ALESS 122.1 has an unusually large gas reservoir. By combining the 38.1 GHz continuum detection of ALESS 122.1 with 1.4 and 5.5 GHz data, we estimate that the freefree contribution to radio emission at 38.1 GHz is 34 ± 17 µJy, yielding a star formation rate (1400 ± 700 Mʘ yr-1) consistent with that from the infrared luminosity. [ABSTRACT FROM AUTHOR]

We present a study of the dust, stars and atomic gas (HI) in an HI-selected sample of local galaxies (z < 0.035) in the Herschel Astrophysical Terahertz Large Area Survey fields. This HI-selected sample reveals a population of very high gas fraction (>80 per cent), low stellar mass sources that appear to be in the earliest stages of their evolution. We compare this sample with dust- and stellar-mass-selected samples to study the dust and gas scaling relations over a wide range of gas fractions (proxy for evolutionary state of a galaxy). The most robust scaling relations for gas and dust are those linked to near-ultraviolet - r (specific star formation rate) and gas fraction; these do not depend on sample selection or environment. At the highest gas fractions, our additional sample shows that the dust content is well below expectations from extrapolating scaling relations for more evolved sources, and dust is not a good tracer of the gas content. The specific dust mass for local galaxies peaks at a gas fraction of ~75 per cent. The atomic gas depletion time is also longer for high gas fraction galaxies, opposite to the trend found for molecular gas depletion time-scale. We link this trend to the changing efficiency of conversion of HI to H2 as galaxies increase in stellar mass surface density during their evolution. Finally, we show that galaxies start out barely obscured and increase in obscuration as they evolve, yet there is no clear and simple link between obscuration and global galaxy properties. [ABSTRACT FROM AUTHOR]

We examine the relationship between star formation and active galactic nuclei (AGN) activity by constructing matched samples of local (0 < z < 0.6) radio-loud and radio-quiet AGN in the Herschel-Astrophysical Terahertz Large Area Survey fields. Radio-loud AGN are classified as high-excitation and low-excitation radio galaxies using their emission lines and WISE 22-µm luminosity. AGN accretion and jet powers in these active galaxies are traced by [O III] emission-line and radio luminosity, respectively. Star formation rates (SFRs) and specific star formation rates (SSFRs) were derived using Herschel 250-µm luminosity and stellar mass measurements from the Sloan Digital Sky Survey-Max Planck Institute for Astrophysics-John Hopkins University catalogue. In the past, star formation studies of AGN have mostly focused on high-redshift sources to observe the thermal dust emission that peaks in the far-infrared, which limited the samples to powerful objects. However, with Herschel we can expand this to low redshifts. Our stacking analyses show that SFRs and SSFRs of both radio-loud and radio-quiet AGN increase with increasing AGN power but that radio-loud AGN tend to have lower SFR. Additionally, radio-quiet AGN are found to have approximately an order of magnitude higher SSFRs than radio-loud AGN for a given level of AGN power. The difference between the star formation properties of radio-loud and -quiet AGN is also seen in samples matched in stellar mass. [ABSTRACT FROM AUTHOR]

We report the blind detection of 12CO emission from a distant red galaxy, HS1700.DRG55. We have used the IRAM Plateau de Bure Interferometer WideX, with its 3.6 GHz of instantaneous dual-polarization bandwidth, to target 12CO(3-2) from galaxies lying in the protocluster at z = 2.300 in the field HS1700+64. If indeed this line in DRG55 is 12CO(3-2), its detection at 104.9 GHz indicates zCO = 2.296. None of the other eight known z ~ 2.30 protocluster galaxies lying within the primary beam (PB) are detected in 12CO, although the limits are ~2 × worse towards the edge of the PB where several lie. The optical/near-IR magnitudes of DRG55 (RAB > 27, KAB = 22.3) mean that optical spectroscopic redshifts are difficult with 10-m-class telescopes, but near-IR redshifts would be feasible. The 24-µm-implied star formation rate (210Mʘ yr-1), stellar mass (~1011 Mʘ) and 12CO line luminosity (3.6 × 1010 Kkms-1 pc²) are comparable to other normal 12CO-detected star-forming galaxies in the literature, although the galaxy is some ~2 mag (~6 ×) fainter in the rest-frame UV than 12CO-detected galaxies at z > 2. The detection of DRG55 in 12CO complements three other 12CO detected UV-bright galaxies in this protocluster from previous studies, and suggests that many optically faint galaxies in the protocluster may host substantial molecular gas reservoirs, and a full blind census of 12CO in this overdense environment is warranted. [ABSTRACT FROM AUTHOR]

MS 0451.6−0305 is a rich galaxy cluster whose strong lensing is particularly prominent at submm wavelengths. We combine new Submillimetre Common-User Bolometer Array (SCUBA)-2 data with imaging from Herschel Spectral and Photometric Imaging Receiver (SPIRE) and PACS and Hubble Space Telescope 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 four), 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 spectral energy distributions to the individual galaxies that contribute to the giant submm arc, constraining their dust temperatures, far-infrared luminosities, and star formation rates (SFRs). The submm arc first identified by SCUBA can now be seen to be composed of at least five distinct sources, four of these within a galaxy group at z ∼ 2.9. Only a handful of lensed galaxy groups at this redshift are expected on the sky, and thus this is a unique opportunity for studying such systems in detail. The total unlensed luminosity for this galaxy group is (3.1 ± 0.3) × 1012 L⊙, which gives an unlensed SFR of (450 ± 50) M⊙ yr−1. This finding suggests that submm source multiplicity, due to physically associated groupings as opposed to chance alignment, extends to fainter flux densities than previously discovered. Many of these systems may also host optical companions undetected in the submm, as is the case here. [ABSTRACT FROM PUBLISHER]

We present Submillimeter Array [C II] 158 μm and Karl G. Jansky Very Large Array 12CO(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 I], water, and [N II], providing some of the best constraints on the properties of the interstellar medium in a galaxy at z > 5. HLS0918 has a total far-infrared (FIR) luminosity LFIR(8–1000 μm) = (1.6 ± 0.1) × 1014L☼ μ–1, where the total magnification μtotal = 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 LFIR, component = (1.1 ± 0.2) × 1013L☼) 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 (ΔV ∼ 500 km s–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. [ABSTRACT FROM AUTHOR]

We analyze new SCUBA-2 submillimeter and archival SPIRE far-infrared imaging of a z = 1.62 cluster, Cl 0218.3–0510, which lies in the UKIRT Infrared Deep Sky Survey/Ultra-Deep Survey 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 ≳1012L☼ 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 ALMA submillimeter continuum observations, which cover 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-normalized 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, MH ∼ –23, the subsequent stronger fading of the more active galaxies means that they will evolve into passive systems at the present day that are less luminous than the descendants of those galaxies that were already passive at z ∼ 1.6 (MH ∼ –20.5 and MH ∼ –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 Cl 0218.3–0510 we are seeing continuing infall of less extreme, but still ultraluminous, star-forming galaxies onto a pre-existing structure. [ABSTRACT FROM AUTHOR]

We study the evolution of the dust temperature of galaxies in the SFR-M• plane up to z ~ 2 using far-infrared and submillimetre observations from the Herschel Space Observatory taken as part of the PACS Evolutionary Probe (PEP) and Herschel Multi-tiered Extragalactic Survey (HerMES) guaranteed time key programmes. Starting from a sample of galaxies with reliable star-formation rates (SFRs), stellar masses (M•) and redshift estimates, we grid the SFR-M• parameter space in several redshift ranges and estimate the mean dust temperature (Tdust) of each SFR-M•-z bin. Dust temperatures are inferred using the stacked far-infrared flux densities (100-500 µm) of our SFR-M•-z bins. At all redshifts, the dust temperature of galaxies smoothly increases with rest-frame infrared luminosities (LIR), specific SFRs (SSFR; i.e., SFR/M•), and distances with respect to the main sequence (MS) of the SFR-M• plane (i.e., ? log (SSFR)MS = log [SSFR(galaxy)/SSFRMS(M•, z)]). The Tdust-SSFR and Tdust - ?log (SSFR)MS correlations are statistically much more significant than the Tdust-LIR one. While the slopes of these three correlations are redshiftindependent, their normalisations evolve smoothly from z = 0 and z ~ 2. We convert these results into a recipe to derive Tdust from SFR, M• and z, valid out to z ~ 2 and for the stellar mass and SFR range covered by our stacking analysis. The existence of a strong Tdust-?log (SSFR)MS correlation provides us with several pieces of information on the dust and gas content of galaxies. Firstly, the slope of the Tdust-?log (SSFR)MS correlation can be explained by the increase in the star-formation efficiency (SFE; SFR/Mgas) with ? log (SSFR)MS as found locally by molecular gas studies. Secondly, at fixed ? log (SSFR)MS, the constant dust temperature observed in galaxies probing wide ranges in SFR and M• can be explained by an increase or decrease in the number of star-forming regions with comparable SFE enclosed in them. And thirdly, at high redshift, the normalisation towards hotter dust temperature of the Tdust-? log (SSFR)MS correlation can be explained by the decrease in the metallicities of galaxies or by the increase in the SFE of MS galaxies. All these results support the hypothesis that the conditions prevailing in the star-forming regions of MS and far-above-MS galaxies are different. MS galaxies have star-forming regions with low SFEs and thus cold dust, while galaxies situated far above the MS seem to be in a starbursting phase characterised by star-forming regions with high SFEs and thus hot dust. [ABSTRACT FROM AUTHOR]

Stellar archaeology shows that massive elliptical galaxies formed rapidly about ten billion years ago with star-formation rates of above several hundred solar masses per year. Their progenitors are probably the submillimetre bright galaxies at redshifts z greater than 2. Although the mean molecular gas mass (5 × 1010 solar masses) of the submillimetre bright galaxies can explain the formation of typical elliptical galaxies, it is inadequate to form elliptical galaxies that already have stellar masses above 2 × 1011 solar masses at z ≈ 2. Here we report multi-wavelength high-resolution observations of a rare merger of two massive submillimetre bright galaxies at z = 2.3. The system is seen to be forming stars at a rate of 2,000 solar masses per year. The star-formation efficiency is an order of magnitude greater than that of normal galaxies, so the gas reservoir will be exhausted and star formation will be quenched in only around 200 million years. At a projected separation of 19 kiloparsecs, the two massive starbursts are about to merge and form a passive elliptical galaxy with a stellar mass of about 4 × 1011 solar masses. We conclude that gas-rich major galaxy mergers with intense star formation can form the most massive elliptical galaxies by z ≈ 1.5. [ABSTRACT FROM AUTHOR]

We have constructed an extended halo model (EHM) which relates the total stellar mass and star-formation rate (SFR) to halo mass (Mh). An empirical relation between the distribution functions of total stellar mass of galaxies and host halo mass, tuned to match the spatial density of galaxies over 0 < z < 2 and the clustering properties at z ∼ 0, is extended to include two different scenarios describing the variation of SFR on Mh. We also present new measurements of the redshift evolution of the average SFR for star-forming galaxies of different stellar masses up to z = 2, using data from the Herschel Multi-tiered Extragalactic Survey for infrared bright galaxies.Combining the EHM with the halo accretion histories from numerical simulations, we trace the stellar mass growth and star-formation history in haloes spanning a range of masses. We find that: (1) the intensity of the star-forming activity in haloes in the probed mass range has steadily decreased from z ∼ 2 to 0; (2) at a given epoch, haloes in the mass range between a few times 1011 M⊙ and a few times 1012 M⊙ are the most efficient at hosting star formation; (3) the peak of SFR density shifts to lower mass haloes over time; and (4) galaxies that are forming stars most actively at z ∼ 2 evolve into quiescent galaxies in today's group environments, strongly supporting previous claims that the most powerful starbursts at z ∼ 2 are progenitors of today's elliptical galaxies. [ABSTRACT FROM AUTHOR]

Dust emission at submillimetre wavelengths allows us to trace the early phases of star formation in the Universe. In order to understand the physical processes involved in this mode of star formation, it is essential to gain knowledge about the dark matter structures – most importantly their masses – that submillimetre galaxies live in. Here we use the magnification effect of gravitational lensing to determine the average mass and dust content of submillimetre galaxies with 250 μm flux densities of S250 > 15 mJy selected using data from the Herschel Multi-tiered Extragalactic Survey. The positions of hundreds of submillimetre foreground lenses are cross-correlated with the positions of background Lyman-break galaxies at z ∼ 3–5 selected using optical data from the Canada–France–Hawaii Telescope Legacy Survey. We detect a cross-correlation signal at the 7σ level over a sky area of 1 deg2, with ∼80 per cent of this signal being due to magnification, whereas the remaining ∼20 per cent comes from dust extinction. Adopting some simple assumptions for the dark matter and dust profiles and the redshift distribution enables us to estimate the average mass of the haloes hosting the submillimetre galaxies to be log 10[M200/M⊙] = 13.17+ 0.05− 0.08(stat.) and their average dust mass fraction (at radii of >10 kpc) to be Mdust/M200 ≈ 6 × 10−5. This supports the picture that submillimetre galaxies are dusty, forming stars at a high rate, reside in massive group-sized haloes and are a crucial phase in the assembly and evolution of structure in the Universe. [ABSTRACT FROM AUTHOR]

We study the far-infrared and sub-millimetre properties of a sample of ultraviolet (UV) selected galaxies at z ∼ 1.5. Using stacking at 250, 350 and 500 μm from Herschel Space Observatory Spectral and Photometric Imaging Receiver (SPIRE) imaging of the Cosmological Evolution Survey (COSMOS) field obtained within the Herschel Multi-tiered Extragalactic Survey (HERMES) key programme, we derive the mean infrared (IR) luminosity as a function of both UV luminosity and slope of the UV continuum β. The IR to UV luminosity ratio is roughly constant over most of the UV luminosity range we explore. We also find that the IR to UV luminosity ratio is correlated with β. We observe a correlation that underestimates the correlation derived from low-redshift starburst galaxies, but is in good agreement with the correlation derived from local normal star-forming galaxies. Using these results we reconstruct the IR luminosity function of our UV-selected sample. This luminosity function recovers the IR luminosity functions measured from IR-selected samples at the faintest luminosities (LIR ∼ 1011 L⊙), but might underestimate them at the bright-end (LIR ≳ 5 × 1011 L⊙). For galaxies with 1011 < LIR/L⊙ < 1013, the IR luminosity function of an UV selection recovers (given the differences in IR-based estimates) 52–65 to 89–112 per cent of the star formation rate density derived from an IR selection. The cosmic star formation rate density derived from this IR luminosity function is 61–76 to 100–133 per cent of the density derived from IR selections at the same epoch. Assuming the latest Herschel results and conservative stacking measurements, we use a toy model to fully reproduce the far-IR luminosity function from our UV selection at z ∼ 1.5. This suggests that a sample around 4 mag deeper (i.e. reaching u* ∼ 30 mag) and a large dispersion of the IR to UV luminosity ratio are required. [ABSTRACT FROM AUTHOR]

Context. A tight correlation exists between far-infrared and radio emission for star-forming galaxies (SFGs), which seems to hold out to high redshifts (z ≈ 2). Any excess of radio emission over that expected from star formation processes is most likely produced by an active galactic nucleus (AGN), often hidden by large amounts of dust and gas. Identifying these radio-excess sources will allow us to study a population of AGN unbiased by obscuration and thus find some of the most obscured, Compton-thick AGN, which are in large part unidentified even in the deepest X-ray and infrared (IR) surveys. Aims. We present here a new spectral energy distribution (SED) fitting approach that we adopt to select radio-excess sources amongst distant star-forming galaxies in the GOODS-Herschel (North) field and to reveal the presence of hidden, highly obscured AGN. Methods. Through extensive SED analysis of 458 galaxies with radio 1.4 GHz and mid-IR 24 μm detections using some of the deepest Chandra X-ray, Spitzer and Herschel infrared, and VLA radio data available to date, we have robustly identified a sample of 51 radio-excess AGN (∼1300 deg-2) out to redshift z ≈ 3. These radio-excess AGN have a significantly lower far-IR/radio ratio (q < 1:68, 3σ) than the typical relation observed for star-forming galaxies (q ≈ 2:2). Results. We find that ≈45% of these radio-excess sources have a dominant AGN component in the mid-IR band, while for the remainders the excess radio emission is the only indicator of AGN activity. The presence of an AGN is also confirmed by the detection of a compact radio core in deep VLBI 1.4 GHz observations for eight of our radio-excess sources (≈16%; ≈66% of the VLBI detected sources in this field), with the excess radio flux measured from our SED analysis agreeing, to within a factor of two, with the radio core emission measured by VLBI. We find that the fraction of radio-excess AGN increases with X-ray luminosity reaching ∼60% at LX ≈ 1044-1045 erg s-1, making these sources an important part of the total AGN population. However, almost half (24/51) of these radio-excess AGN are not detected in the deep Chandra X-ray data, suggesting that some of these sources might be heavily obscured. Amongst the radio-excess AGN we can distinguish three groups of objects: i) AGN clearly identified in infrared (and often in X-rays), a fraction of which are likely to be distant Compton-thick AGN; ii) moderate luminosity AGN (LX≲ . 1043 erg s-1) hosted in strong star-forming galaxies; and iii) a small fraction of low accretion-rate AGN hosted in passive (i.e. weak or no star-forming) galaxies. We also find that the specific star formation rates (sSFRs) of the radio-excess AGN are on average lower that those observed for X-ray selected AGN hosts, indicating that our sources are forming stars more slowly than typical AGN hosts, and possibly their star formation is progressively quenching. [ABSTRACT FROM AUTHOR]

ABSTRACT We have used data from the Herschel Astrophysical Terahertz Large-Area Survey (H-ATLAS) at 250, 350 and 500 [ABSTRACT FROM AUTHOR]

ABSTRACT This paper describes Herschel observations of the nearby (8.5 pc) G5V multi-exoplanet host star 61 Vir at 70, 100, 160, 250, 350 and 500 m carried out as part of the DEBRIS survey. These observations reveal emission that is significantly extended out to a distance of >15 arcsec with a morphology that can be fitted by a nearly edge-on (77° inclination) radially broad (from 30 au out to at least 100 au) debris disc of fractional luminosity 2.7 × 10−5, with two additional (presumably unrelated) sources nearby that become more prominent at longer wavelengths. Chance alignment with a background object seen at 1.4 GHz provides potential for confusion, however, the star's 1.4 arcsec yr−1 proper motion allows archival Spitzer 70 m images to confirm that what we are interpreting as disc emission really is circumstellar. Although the exact shape of the disc's inner edge is not well constrained, the region inside 30 au must be significantly depleted in planetesimals. This is readily explained if there are additional planets outside those already known (i.e. in the 0.5-30 au region), but is also consistent with collisional erosion. We also find tentative evidence that the presence of detectable debris around nearby stars correlates with the presence of the lowest mass planets that are detectable in current radial velocity surveys. Out of an unbiased sample of the nearest 60 G stars, 11 are known to have planets, of which six (including 61 Vir) have planets that are all less massive than Saturn, and four of these have evidence for debris. The debris towards one of these planet hosts (HD 20794) is reported here for the first time. This fraction (4/6) is higher than that expected for nearby field stars (15 per cent), and implies that systems that form low-mass planets are also able to retain bright debris discs. We suggest that this correlation could arise because such planetary systems are dynamically stable and include regions that are populated with planetesimals in the formation process where the planetesimals can remain unperturbed over Gyr time-scales. [ABSTRACT FROM AUTHOR]

ABSTRACT We present a spectroscopic catalogue of 40 luminous starburst galaxies at z= 0.7-1.7 (median z= 1.3). 19 of these are submillimetre galaxies (SMGs) and 21 are submillimetre-faint radio galaxies (SFRGs). This sample helps us to fill in the redshift desert at z= 1.2-1.7 in previous studies as well as to probe a lower luminosity population of galaxies. Radio fluxes are used to determine star formation rates for our sample which range from around 50-500 M⊙ yr−1 and are generally lower than those in z∼ 2 SMGs. We identify nebular [O ii] 3727 emission in the rest-UV spectra and use the linewidths to show that SMGs and SFRGs in our sample have larger linewidths and therefore dynamical masses than optically selected star-forming galaxies at similar redshifts. The linewidths are indistinguishable from those measured in the z∼ 2 SMG populations suggesting little evolution in the dynamical masses of the galaxies between redshift 1 and 2. [Ne v] and [Ne iii] emission lines are identified in a subset of the spectra indicating the presence of an active galactic nucleus (AGN). In addition, a host of interstellar absorption lines corresponding to transitions of Mg ii and Fe ii ions are also detected. These features show up prominently in composite spectra and we use these composites to demonstrate that the absorption lines are present at an average blueshift of −240 ± 50 km s−1 relative to the systemic velocities of the galaxies derived from [O ii]. This indicates the presence of large-scale outflowing interstellar gas in these systems. We do not find any evidence for differences in outflow velocities between SMGs and SFRGs of similar infrared luminosities. We find that the outflow velocities of z∼ 1.3 SMGs and SFRGs are consistent with the V∝ SFR0.3 local envelope seen in lower redshift ultraluminous infrared galaxies (ULIRGs). These observations are well explained by a momentum-driven wind model. [ABSTRACT FROM AUTHOR]

ABSTRACT For the first time, we investigate the X-ray/infrared (IR) correlation for star-forming galaxies (SFGs) at z∼ 1, using SPIRE submm data from the recently launched Herschel Space Observatory and deep X-ray data from the 2-Ms Chandra Deep Field-North survey. We examine the X-ray/IR correlation in the soft X-ray (SX; 0.5-2 keV) and hard X-ray (HX; 2-10 keV) bands by comparing our z∼ 1 SPIRE-detected SFGs to equivalently IR-luminous ( LIR > 1010 L⊙) samples in the local/low-redshift Universe. Our results suggest that the X-ray/IR properties of the SPIRE SFGs are on average similar to those of their local counterparts, as we find no evidence for evolution in the LSX/ LIR and LHX/ LIR ratios with redshift. We note, however, that at all redshifts, both LSX/ LIR and LHX/ LIR are strongly dependent on IR luminosity, with luminous and ultraluminous IR galaxies (LIRGs and ULIRGs; LIR > 1011 L⊙) having up to an order of magnitude lower values than normal IR galaxies ( LIR < 1011 L⊙). We derive a LSX- LIR relation and confirm the applicability of an existing LHX- LIR relation for both local and distant LIRGs and ULIRGs, consistent with a scenario where X-ray luminosity is correlated with the star formation rate. [ABSTRACT FROM AUTHOR]

ABSTRACT We report the detection of a significant excess in the surface density of far-infrared sources from the Herschel-Astrophysical Terahertz Large Area Survey within ∼1 Mpc of the centres of 66 optically selected clusters of galaxies in the Sloan Digital Sky Survey with 〈 z〉∼ 0.25. From the analysis of the multiwavelength properties of their counterparts we conclude that the far-infrared emission is associated with dust-obscured star formation and/or active galactic nuclei (AGN) within galaxies in the clusters themselves. The excess reaches a maximum at a radius of ∼0.8 Mpc, where we find 1.0 ± 0.3 S250 > 34 mJy sources on average per cluster above what would be expected for random field locations. If the far-infrared emission is dominated by star formation (as opposed to AGN) then this corresponds to an average star formation rate of ∼7 M ⊙ yr−1 per cluster in sources with LIR > 5 × 1010 L ⊙. Although lensed sources make a negligible contribution to the excess signal, a fraction of the sources around the clusters could be gravitationally lensed, and we have identified a sample of potential cases of cluster-lensed Herschel sources that could be targeted in follow-up studies. [ABSTRACT FROM AUTHOR]