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Wide, deep, blind continuum surveys at submillimetre/millimetre (submm/mm) wavelengths are required to provide a full inventory of the dusty, distant Universe. However, conducting such surveys to the necessary depth, with sub-arcsec angular resolution, is prohibitively time-consuming, even for the most advanced submm/mm telescopes. Here, we report the most recent results from the ALMACAL project, which exploits the 'free' calibration data from the Atacama Large Millimetre/submillimetre Array (ALMA) to map the lines of sight towards and beyond the ALMA calibrators. ALMACAL has now covered 1001 calibrators, with a total sky coverage around 0.3 deg2, distributed across the sky accessible from the Atacama desert, and has accumulated more than 1000 h of integration. The depth reached by combining multiple visits to each field makes ALMACAL capable of searching for faint, dusty, star-forming galaxies (DSFGs), with detections at multiple frequencies to constrain the emission mechanism. Based on the most up-to-date ALMACAL data base, we report the detection of 186 DSFGs with flux densities down to S 870 µm ∼ 0.2 mJy, comparable with existing ALMA large surveys but less susceptible to cosmic variance. We report the number counts at five wavelengths between 870  μ m and 3 mm, in ALMA bands 3, 4, 5, 6, and 7, providing a benchmark for models of galaxy formation and evolution. By integrating the observed number counts and the best-fitting functions, we also present the resolved fraction of the cosmic infrared background (CIB) and the CIB spectral shape. Combining existing surveys, ALMA has currently resolved about half of the CIB in the submm/mm regime. [ABSTRACT FROM AUTHOR]

Variations in the dust emissivity index, |$\beta$|⁠ , within and between galaxies, are evidence that the chemistry and physics of dust must vary on large scales, although the nature of the physical and/or chemical variations is still unknown. In this paper, we estimate values of |$\beta$| and dust temperature for a sample of 109 dusty star-forming galaxies (DSFGs) over the range, |$2 \ \lt\ z \ \lt\ 6$|⁠. We compare the results obtained with both an optically thin model and a general opacity model, finding that our estimates of |$\beta$| are similar between the models but our estimates of dust temperature are not. We find no evidence of a change in |$\beta$| with redshift, with a median value of |$\beta = 1.96$| for the optically thin model with a confidence interval (16–84 per cent) of 1.67 to 2.35 for the population. Using simulations, we estimate the measurement errors from our procedure and show that the variation of |$\beta$| in the population results from intrinsic variations in the properties of the dust in DSFGs. At a fixed far-infrared luminosity, we find no evidence for a change in dust temperature, |$T_{\textrm {dust}}$|⁠ , with redshift. After allowing for the effects of correlated measurement errors, we find an inverse correlation between |$\beta$| and |$T_{\textrm {dust}}$| in DSFGs, for which there is also evidence in low-redshift galaxies. [ABSTRACT FROM AUTHOR]

With the spatial resolution of the Atacama Large Millimetre Array (ALMA), dusty galaxies in the distant Universe typically appear as single, compact blobs of dust emission, with a median half-light radius, ≈1 kpc. Occasionally, strong gravitational lensing by foreground galaxies or galaxy clusters has probed spatial scales 1–2 orders of magnitude smaller, often revealing late-stage mergers, sometimes with tantalizing hints of sub-structure. One lensed galaxy in particular, the Cosmic Eyelash at z = 2.3, has been cited extensively as an example of where the interstellar medium exhibits obvious, pronounced clumps, on a spatial scale of ≈100 pc. Seven orders of magnitude more luminous than giant molecular clouds in the local Universe, these features are presented as circumstantial evidence that the blue clumps observed in many z ∼ 2–3 galaxies are important sites of ongoing star formation, with significant masses of gas and stars. Here, we present data from ALMA which reveal that the dust continuum of the Cosmic Eyelash is in fact smooth and can be reproduced using two Sérsic profiles with effective radii, 1.2 and 4.4 kpc, with no evidence of significant star-forming clumps down to a spatial scale of ≈80 pc and a star formation rate of <3 M⊙ yr−1. [ABSTRACT FROM AUTHOR]

HATLAS J084933.4 + 021443 was identified as a dusty starburst via its rest-frame far-infrared (far-IR) emission. Multifrequency imaging and spectroscopy revealed a cluster of four dusty galaxies at z  = 2.41, covering 80 kpc. Here, we use Atacama Large Millimetre Array to confirm a more distant, fifth protocluster member, and present X-ray and rest-frame optical imaging spectroscopy of the brightest, an unlensed hyperluminous IR galaxy (HyLIRG). The data reveal broad Hα and bright [N  ii ] lines, and bright X-ray emission, characteristics that betray a Type-1 active galactic nucleus (AGN), strengthening evidence that AGN are ubiquitous amongst HyLIRGs. The accreting black hole is supermassive, M bh ≈ 2 × 109 M⊙, with little intrinsic absorption, N H ≈ 5 × 1021 cm−2. The X-ray properties suggest the accretion luminosity rivals that of the starburst, yet it is not obvious where this emerges in its panchromatic spectral energy distribution. We outline three scenarios that could give rise to the observed characteristics, and how we might distinguish between them. In the first, we see the AGN through the host galaxy because of the cavity it excavates. In the others, the AGN is not cospatial with the starburst, having been ejected via asymmetric gravitational radiation, or having evolved towards the naked quasar phase in an unseen companion. [ABSTRACT FROM AUTHOR]

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 1.3- and/or 3-mm continuum images and 3-mm spectral scans, obtained using Northern Extended Millimeter Array (NOEMA) and Atacama Large Millimeter Array (ALMA), of 21 distant, dusty, star-forming galaxies. Our sample is a subset of the galaxies selected by Ivison et al. on the basis of their extremely red far-infrared (far-IR) colours and low Herschel flux densities; most are thus expected to be unlensed, extraordinarily luminous starbursts at z ≳ 4, modulo the considerable cross-section to gravitational lensing implied by their redshift. We observed 17 of these galaxies with NOEMA and four with ALMA, scanning through the 3-mm atmospheric window. We have obtained secure redshifts for seven galaxies via detection of multiple CO lines, one of them a lensed system at z = 6.027 (two others are also found to be lensed); a single emission line was detected in another four galaxies, one of which has been shown elsewhere to lie at z = 4.002. Where we find no spectroscopic redshifts, the galaxies are generally less luminous by 0.3-0.4 dex, which goes some way to explaining our failure to detect line emission. We show that this sample contains the most luminous known star-forming galaxies. Due to their extreme star-formation activity, these galaxies will consume their molecular gas in ≲ 100 Myr, despite their high molecular gas masses, and are therefore plausible progenitors of the massive, 'red-and-dead' elliptical galaxies at z ≈ 3. [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 results from a 19-h integration with the Spectral and Photometric Imaging REceiver (SPIRE) Fourier Transform Spectrometer aboard the Herschel Space Observatory which has revealed the presence of a molecular outflow from the Cosmic Eyelash (SMM J2135−0102) via the detection of blueshifted OH absorption. Detections of several fine-structure emission lines indicate low-excitation H ii regions contribute strongly to the [C ii] luminosity in this z = 2.3 ultra-luminous infrared galaxy (ULIRG). The OH feature suggests a maximum wind velocity of 700 km s− 1, which is lower than the expected escape velocity of the host dark matter halo, ≈ 1000 km s− 1. A large fraction of the available molecular gas could thus be converted into stars via a burst protracted by the resulting gas fountain, until an active galactic nucleus (AGN)-driven outflow can eject the remaining gas. [ABSTRACT FROM AUTHOR]

ABSTRACT We present a study using the Karl G. Jansky Very Large Array (VLA) of 12CO J = 1−0 emission in three strongly lensed submillimetre-selected galaxies (SMM J16359, SMM J14009 and SMM J02399) at z = 2.5-2.9. These galaxies span LIR = 1011-1013 L⊙, offering an opportunity to compare the interstellar medium of luminous infrared galaxies and ultraluminous infrared galaxies at high redshift. We estimate molecular gas masses in the range of 2-40 × 109 M⊙ using a method that assumes canonical underlying brightness temperature ( Tb) ratios for star-forming and non-star-forming gas phases and a maximal star formation efficiency. A more simplistic method - using XCO = 0.8 and the measured Tb ratios - yields gas masses twice as high. In SMM J14009 we find [ABSTRACT FROM AUTHOR]

ABSTRACT We report new, sensitive observations of two z ∼ 3-3.5 far-infrared-luminous radio galaxies, 6C 1909+72 and B3 J2330+3927, in the 12CO J = 1−0 transition with the Karl Jansky Very Large Array and at 100-500 m using Herschel, alongside new and archival 12CO J = 4−3 observations from the Plateau de Bure Interferometer. We introduce a new colour-colour diagnostic plot to constrain the redshifts of several distant, dusty galaxies in our target fields. A bright SMG near 6C 1909+72 likely shares the same node or filament as the signpost active galactic nuclei (AGN), but it is not detected in 12CO despite ∼20 000 km s−1 of velocity coverage. Also in the 6C 1909+72 field, a large, red dust feature spanning ≈500 kpc is aligned with the radio jet. We suggest several processes by which metal-rich material may have been transported, favouring a collimated outflow reminiscent of the jet-oriented metal enrichment seen in local cluster environments. Our interferometric imaging reveals a gas-rich companion to B3 J2330+3927; indeed, all bar one of the eight z ≳ 2 radio galaxies (or companions) detected in 12CO provide some evidence that starburst activity in radio-loud AGN at high redshift is driven by the interaction of two or more gas-rich systems in which a significant mass of stars has already formed, rather than via steady accretion of cold gas from the cosmic web. We find that the 12CO brightness temperature ratios in radio-loud AGN host galaxies are significantly higher than those seen in similarly intense starbursts where AGN activity is less pronounced. Our most extreme example, where [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]

ABSTRACT We investigate the potential of submm-mm and submm-mm-radio photometric redshifts using a sample of mm-selected sources as seen at 250, 350 and 500μm by the SPIRE instrument on Herschel. From a sample of 63 previously identified mm sources with reliable radio identifications in the Great Observatories Origins Deep Survey North and Lockman Hole North fields, 46 (73 per cent) are found to have detections in at least one SPIRE band. We explore the observed submm/mm colour evolution with redshift, finding that the colours of mm sources are adequately described by a modified blackbody with constant optical depth τ= (ν/ nu0)β, where β=+1.8 and ν0= c/100 μm. We find a tight correlation between dust temperature and IR luminosity. Using a single model of the dust temperature and IR luminosity relation, we derive photometric redshift estimates for the 46 SPIRE-detected mm sources. Testing against the 22 sources with known spectroscopic or good quality optical/near-IR photometric redshifts, we find submm/mm photometric redshifts offer a redshift accuracy of |Δ z|/(1 + z) = 0.16 (〈|Δ z|〉= 0.51). Including constraints from the radio-far-IR correlation, the accuracy is improved to |Δ z|/(1 + z) = 0.15 (〈|Δ z|〉= 0.45). We estimate the redshift distribution of mm-selected sources finding a significant excess at z > 3 when compared to ∼ 850 μm selected samples. [ABSTRACT FROM AUTHOR]

We present radio and infrared (3.6-24 m) counterparts to submillimetre galaxies (SMGs) detected in the Extended Chandra Deep Field-South with the Large APEX Bolometer Camera (LABOCA) 870-m bolometer camera on the 12-m Atacama Pathfinder Experiment. Using the Very Large Array at 1.4 GHz and Spitzer, we have identified secure counterparts to 79 of the 126 SMGs [signal-to-noise ratio mJy] in the field, 62 via their radio and/or 24-m emission, the remainder using a colour-flux cut on Infrared Array Camera 3.6- and 5.8-m sources chosen to maximize the number of secure, coincident radio and 24-m counterparts. In constructing our radio catalogue, we have corrected for the effects of 'flux boosting', then used the corrected flux densities to estimate the redshifts of the SMGs based on the radio/submm spectral indices. The effect of the boosting correction is to increase the median redshift by 0.2 resulting in a value of (1 errors) for the secure radio counterparts, in agreement with other studies, both spectroscopic and photometric. [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 describe the reduction of data taken with the PACS instrument on board the Herschel Space Observatory in the Science Demonstration Phase of the Herschel-ATLAS ( H-ATLAS) survey, specifically data obtained for a deg region using Herschel's fast-scan (60 arcsec s) parallel mode. We describe in detail a pipeline for data reduction using customized procedures within from data retrieval to the production of science-quality images. We found that the standard procedure for removing cosmic ray glitches also removed parts of bright sources and so implemented an effective two-stage process to minimize these problems. The pronounced noise is removed from the timelines using 3.4- and 2.5-arcmin boxcar high-pass filters at 100 and 160 μm. Empirical measurements of the point spread function (PSF) are used to determine the encircled energy fraction as a function of aperture size. For the 100- and 160-μm bands, the effective PSFs are ∼9 and ∼13 arcsec (FWHM), and the 90-per cent encircled energy radii are 13 and 18 arcsec. Astrometric accuracy is good to ≲2 arcsec. The noise in the final maps is correlated between neighbouring pixels and rather higher than advertised prior to launch. For a pair of cross-scans, the 5σ point-source sensitivities are 125-165 mJy for 9-13 arcsec radius apertures at 100 μm and 150-240 mJy for 13-18 arcsec radius apertures at 160 μm. [ABSTRACT FROM AUTHOR]

We present the first study of the far-infrared (FIR) properties of high-redshift, radio-selected ultraluminous infrared galaxies (ULIRGs) using deep observations obtained with the Spectral and Photometric Imaging Receiver (SPIRE) from the Herschel Multi-tiered Extragalactic Survey (HerMES). These galaxies span a large range of 850-m fluxes from submillimetre-luminous 10 mJy sources (SCUBA galaxies) to 1.5 mJy from stacked SCUBA non-detections, thus likely representing a complete distribution of ULIRG spectral energy distributions (SEDs). From Keck spectroscopic surveys in the Lockman-North field we identified a sample of 31 submillimetre galaxies (SMGs) and 37 submillimetre-faint, optically faint radio galaxies (OFRGs), all with radio-inferred IR luminosities L. These galaxies were cross-identified with SPIRE 250-, 350- and 500-m catalogues based on fluxes extracted at 24-m positions in the SWIRE survey, yielding a sample of more than half of the galaxies well detected in at least two of the SPIRE bandpasses. By fitting greybody dust models to the SPIRE photometry together with SCUBA 850-m measurements (for OFRGs, only 850- upper limits), we infer dust temperatures and FIR luminosities. The OFRGs detected by SPIRE have median K and the SMGs have K, both in reasonable agreement with previous (pre- Herschel) estimates, reaffirming that the local FIR/radio correlation holds (at least for this subset of high- ULIRGs) at high redshift (we measure using derived from greybody fit coupled with a power-law extrapolation to the 24 m). Our observations first confirm that a substantial fraction of OFRGs exhibits large infrared luminosities corresponding to SFRs of 400 M yr. The SPIRE observations secondly confirm the higher dust temperatures for these OFRGs than similarly selected SMGs, consistent with early predictions of the submillimetre-faint radio populations. Our observations also clearly confirm the large infrared luminosities of most SMGs selected with mJy and radio and strong 24-m detections, corresponding to SFRs of 700 M yr. [ABSTRACT FROM AUTHOR]

We present new multiwavelength observations of the first submillimetre-selected galaxy (SMG) SMM J 0136 at . These observations include mapping of the CO J= 0 emission using elements of the Expanded Very Large Array, as well as high-resolution 1.4-GHz imaging and optical/infrared (IR) data from the Very Large Array, Hubble Space Telescope, Spitzer and Keck-I. Together, these new data provide fundamental insights into the mass and distribution of stars, gas and dust within this archetypal SMG. The CO J= 0 emission, with its minimal excitation and density requirements, traces the bulk of the metal-rich molecular gas, and reveals a molecular gas mass of , extending over approximately 5 arcsec (∼25 kpc in the source plane), although there is tentative evidence that it may be significantly larger. Our data suggest that three or more distinct structures are encompassed by this molecular gas reservoir, including the broad absorption line (BAL) quasar from which the redshift of the SMG was initially determined. In particular, the new rest-frame near-IR observations identify a massive, obscured, starburst which is coincident with a previously known Lyα cloud. This starburst dominates the far-IR emission from the system and requires a re-assessment of previous claims that the gas reservoir resides in a massive, extended disc around the BAL quasi-stellar object (QSO). Instead, it appears that SMM J 0136 comprises a merger between a far-IR-luminous, but highly obscured starburst, the BAL QSO host and a faint third component. Our findings suggest that this archetypal SMG and its immediate environment mark a vast and complex galactic nursery and that detailed studies of other SMGs are likely to uncover a similarly rich diversity of properties. [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 employed the Giant Metre-wave Radio Telescope and the Very Large Array to map the Lockman Hole. At 610 and 1400 MHz, we reach noise levels of 15 and 6 μJy beam−1, respectively, with well-matched resolutions (∼5 arcsec). At this depth, we obtained reliable detections for about half of the known sub-mm galaxies (SMGs) in the field. For radio-identified SMGs, which are typically at , we measure a mean radio spectral index of (where ) and standard deviation of 0.29, between approximate rest-frame frequencies of 1.8 and 4.2 GHz. The slope of their continuum emission is indistinguishable from that of local star-forming galaxies and suggests that extended optically thin synchrotron emission dominates the radio output of SMGs. Cooling effects by synchrotron emission and Inverse Compton scattering off the cosmic microwave background do not seem to affect their radio spectral energy distributions. For those SMGs judged by Spitzer mid-infrared colours and spectroscopy to host obscured active galactic nuclei (AGN), we find a clear deviation from the rest of the sample – they typically have steeper radio spectral indices, . These findings suggest these mid-IR-/AGN-selected SMGs may have an intrinsically different injection mechanism for relativistic particles, or they might reside in denser environments. This work provides a reliable spectral template for the estimation of far-IR/radio photometric redshifts, and will enable accurate statistical K-corrections for the large samples of SMGs expected with SCUBA-2 and Herschel. [ABSTRACT FROM AUTHOR]

In the run up to routine observations with the upcoming generation of radio facilities, the nature of sub-mJy radio population has been hotly debated. Here, we describe multi-frequency data designed to probe the emission mechanism that dominates in these faint radio sources. Our analysis is based on observations of the Lockman Hole using the Giant Metrewave Radio Telescope (GMRT) – the deepest 610-MHz imaging yet reported – together with 1.4-GHz imaging from the Very Large Array (VLA), well matched in resolution and sensitivity to the GMRT data: , full width at half-maximum (FWHM) . The GMRT and VLA data are cross-matched to obtain the radio spectral indices for the faint radio emitters. Statistical analyses show no clear evolution for the median spectral index, (where ), as a function of flux density. is found to be approximately −0.6 to −0.7, based on an almost unbiased 10σ criterion, down to a flux level of . The fraction of inverted spectrum sources is less than 10 per cent. The results suggest that the most prevalent emission mechanism in the sub-mJy regime is optically thin synchrotron, ruling out a dominant flat spectrum or ultra-steep spectrum radio population. The spectral index distribution has a significant scatter, , which suggests a mixture of different populations at all flux levels. Spectroscopic classification of radio sources with X-ray emission has allowed us to estimate that the fraction of radio-quiet active galactic nuclei (AGN) at is roughly per cent, suggesting that star-forming galaxies dominate the sub-mJy regime. [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]

High-resolution submillimetre (submm) imaging of the high-redshift radio galaxy (HzRG), 4C 60.07, at , has revealed two dusty components of roughly equal integrated flux. Spitzer imaging shows that one of these components (‘B’) is coincident with an extremely red active galactic nucleus (AGN), offset by ∼4 arcsec (∼30 kpc) from the HzRG core. The other submm component (‘A’) – resolved by our synthesized beam and devoid of emission at 3.6–8.0μm – lies between ‘B’ and the HzRG core. Since the radio galaxy was discovered via its extremely young, steep-spectrum radio lobes and the creation of these lobes was likely triggered by the interaction, we argue that we are witnessing an early-stage merger, prior to its eventual equilibrium state. The interaction is between the host galaxy of an actively fuelled black hole (BH) and a gas-rich starburst/AGN (‘B’) marked by the compact submm component and coincident with broad CO(4–3) emission. The second submm component (‘A’) is a plume of cold, dusty gas, associated with a narrow (∼150 km s−1) CO feature, and may represent a short-lived tidal structure. It has been claimed that HzRGs and submillimetre-selected galaxies (SMGs) differ only in the activity of their AGNs, but such complex submm morphologies are seen only rarely amongst SMGs, which are usually older, more relaxed systems. Our study has important implications: where a galaxy's gas reservoir is not aligned with its central BH, CO may be an unreliable probe of dynamical mass, affecting work on the co-assembly of BHs and host spheroids. Our data support the picture wherein close binary AGN are induced by mergers. They also raise the possibility that some supposedly jet-induced starbursts may have formed co-evally (yet independently of) the radio jets, both triggered by the same interaction. Finally, we note that the HzRG host would have gone unnoticed without its jets and its companion, so there may be many other unseen BHs at high redshift, lost in the sea of similarly bright Infrared Array Camera (IRAC) sources – sufficiently massive to drive a -W radio source, yet practically invisible unless actively fuelled. [ABSTRACT FROM AUTHOR]

We have produced sensitive, high-resolution radio maps of 12 submillimetre (submm) galaxies (SMGs) in the Lockman Hole using combined Multi-Element Radio Linked Interferometer Network (MERLIN) and Very Large Array (VLA) data at a frequency of 1.4 GHz. Integrating for 350 h yielded an rms noise of 6.0 μJy beam−1 and a resolution of 0.2–0.5 arcsec. For the first time, wide-field data from the two arrays have been combined in the ( u, v) plane and the bandwidth smearing response of the VLA data has been removed. All of the SMGs are detected in our maps as well as sources comprising a non-submm luminous control sample. We find evidence that SMGs are more extended than the general μJy radio population and that therefore, unlike in local ultraluminous infrared galaxies (ULIRGs), the starburst component of the radio emission is extended and not confined to the galactic nucleus. For the eight sources with redshifts we measure linear sizes between 1 and 8 kpc with a median of 5 kpc. Therefore, they are in general larger than local ULIRGs which may support an early-stage merger scenario for the starburst trigger. X-rays betray active galactic nuclei (AGN) in six of the 33 sources in the combined sample. All but one of these are in the control sample, suggesting a lower incidence of AGN amongst the submm-luminous galaxies which is, in turn, consistent with increased X-ray absorption in these dust-obscured starbursts. Only one of our sources is resolved into multiple, distinct components with our high-resolution data. Finally, compared to a previous study of faint radio sources in the GOODS-N field we find systematically smaller source sizes and no evidence for a tail extending to ∼4 arcsec. Possible reasons for this are discussed. [ABSTRACT FROM AUTHOR]

We present submillimetre (submm) continuum images of the fields of three luminous quasars at z > 5, obtained at 850 and 450 μm using the Submillimetre Common-User Bolometer Array on the James Clerk Maxwell Telescope (JCMT). N-body simulations predict that such quasars evolve to become the central dominant galaxies of massive clusters at , but at z= 5–6 they are actively forming stars and surrounded by a rich protofilamentary structure of young galaxies. Our purpose in taking these images was to search for other luminous, star-forming galaxies in the vicinity of the signpost active galactic nuclei and thus associated with such a protocluster. Two of the quasar host galaxies are luminous submm galaxies (SMGs) in their own right, implying star formation rates . Despite the coarse 850-μm beam of the JCMT, our images show evidence of extended emission on a scale of ∼100 kpc from at least one quasar – indicative of a partially resolved merger or a colossal host galaxy. In addition, at >3σ significance we detect 12 (5) SMGs at 850 μm (450 μm) in the surrounding fields. Number counts of these SMGs are comparable with those detected in the fields of radio galaxies, and both samples are, at the bright end, overabundant by a factor of ≈4 relative to blank-field submm surveys. Whilst the redshift-sensitive 850 μm/450 μm and 850 μm/1.4 GHz flux density ratios indicate that some of these SMGs are likely foreground objects, the counts suggest that ∼60 per cent lie in the same large-scale structures as the quasars. [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]

We present catalogues of faint 1.4-GHz radio sources from extremely deep Very Large Array pointings in the Lockman Hole, the Hubble Deep Field-North (HDF-N) and the European Large Area ISO Survey (ELAIS) N2 field. Our analysis of the HDF-N data has produced maps that are significantly deeper than those previously published, and we have used these to search for counterparts to submillimetre sources. For each of the fields, we have derived normalized differential source counts and in the case of the HDF-N find no evidence for the previously reported underdensity of sources; our counts are entirely consistent with those found for the majority of other fields. The catalogues are available as an online supplement to this paper and the maps are also available for download. [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]

The modest significance of most sources detected in current (sub)millimetre [(sub)mm] surveys can potentially compromise some analyses due to the inclusion of spurious sources in catalogues typically selected at ≥3.0–3.5σ. Here, we develop and apply a dual-survey extraction technique to Submillimetre Common-User Bolometer Array (SCUBA) and Max-Planck Millimetre Bolometer (MAMBO) images of the Lockman Hole. Cut above 5σ, our catalogue of submillimetre galaxies (SMGs) is more robust than previous samples, with a reduced likelihood of real, but faint SMGs (beneath and around the confusion limit) entering via superposition with noise. Our selection technique yields 19 SMGs in an effective area of 165 arcmin2, of which we expect at most two to be due to chance superposition of SCUBA and MAMBO noise peaks. The effective flux limit of the survey (∼4 mJy at ∼1 mm) is well matched to our deep 1.4-GHz image . The former is sensitive to luminous, dusty galaxies at extreme redshifts whilst the latter probes the regime. A high fraction of our robust SMGs (∼80 per cent) have radio counterparts which, given the ∼10 per cent contamination by spurious sources, suggests that very distant SMGs are unlikely to make up more than ∼10 per cent of the bright SMG population. This implies that almost all of the SMG population is amenable to study via the deepest current radio imaging. We use these radio counterparts to provide an empirical calibration of the positional uncertainty in SMG catalogues. We then go on to outline the acquisition of redshifts for radio-identified SMGs, from sample selection in the submm, to counterpart selection in the radio and optical/infrared, to slit placement on spectrograph masks. We determine a median of from a sample of six secure redshifts for unambiguous radio-identified submm sources and when we include submm sources with multiple radio counterparts and/or less reliable redshifts. These figures are consistent with previous estimates, suggesting that our knowledge of the median redshift of bright SMG population has not been biased by the low significance of the source catalogues employed. [ABSTRACT FROM AUTHOR]

We have investigated the rest-frame optical and far-infrared properties of a sample of extremely bright candidate Lyman-break galaxies (LBGs) identified in the Sloan Digital Sky Survey. Their high ultraviolet luminosities and lack of strong ultraviolet emission lines are suggestive of massive starbursts, although it is possible that they are more typical luminosity LBGs which have been highly magnified by strong gravitational lensing. Alternatively, they may be an unusual class of weak-lined quasars. If the ultraviolet and submillimetre (submm) properties of these objects mirror those of less luminous, starburst LBGs, then they should have detectable rest-frame far-infrared emission. However, our submm photometry fails to detect such emission, indicating that these systems are not merely scaled-up (either intrinsically or as a result of lensing) examples of typical LBGs. In addition we have searched for the morphological signatures of strong lensing, using high-resolution, near-infrared imaging, but we find none. Instead, near-infrared spectroscopy reveals that these systems are, in fact, a rare class of broad absorption line quasars. [ABSTRACT FROM AUTHOR]

The SCUBA 8-mJy survey is the largest submillimetre (submm) extragalactic mapping survey undertaken to date, covering 260 arcmin² to a 4σ detection limit of ...8 mJy at 850 µm, centred on the Lockman Hole and ELAIS N2 regions. Here, we present the results of new 1.4GHz imaging of these fields, of the depth and resolution necessary to reliably identify radio counterparts for 18 of 30 submm sources, with possible detections of a further 25 per cent. Armed with this greatly improved positional information, we present and analyse new optical, near-infrared (near-IR) and XMM-Newton X-ray imaging to identify optical/IR host galaxies to half of the submm-selected sources in those fields. As many as 15 per cent of the submm sources detected at 1.4 GHz are resolved by the 1.4-arcsec beam and a further 25 per cent have more than one radio counterpart, suggesting that radio and submm emission arise from extended starbursts and that interactions are common. We note that less than a quarter of the submm-selected sample would have been recovered by targeting optically faint radio sources, underlining the selective nature of such surveys. At least 60 per cent of the radio-confirmed optical/IR host galaxies appear to be morphologically distorted; many are composite systems — red galaxies with relatively blue companions; just over one half are found to be very red (I - K > 3.3) or extremely red (I - K > 4); contrary to popular belief, most are sufficiently bright to be tackled with spectrographs on 8-m telescopes. We find one submm source which is associated with the steep-spectrum lobe of a radio galaxy, at least two more with flatter radio spectra typical of radio-loud active galactic nuclei (AGN), one of them variable. The latter is amongst four sources (≡ 15 per cent of the full sample) with X-ray emission consistent with obscured AGN, though the AGN would need to be Compton thick to power the observed far-IR luminosity. We exploit our... [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]

We present a detailed multiwavelength study (from rest-frame ultraviolet to far-infrared) of narrow-band selected, star-forming (SF) Hα emitters (HAEs) at z ~ 2.23 taken from the High-Redshift(Z) Emission Line Survey (HiZELS). We find that HAEs have similar properties and colours derived from spectral energy distributions as sBzK galaxies, and probe a well-defined portion of the SF population at z ~ 2. This is not true for Lyα emitters (LAEs), which are strongly biased towards blue, less massive galaxies (missing a significant percentage of the SF population). Combining our Hα observations with matched, existing Lyα data, we determine that the Lyα escape fraction (fesc) is low (only ~4.5 percent of HAEs show Lyα emission) and decreases with increasing dust attenuation, ultraviolet continuum slope, stellar mass and star formation rate (SFR). This suggests that Lyα preferentially escapes from blue galaxies with low dust attenuation. However, a small population of red and massive LAEs is also present, in agreement with previous works and indicating that dust and Lyα are not mutually exclusive. Using different and completely independent measures of the total SFR, we show that the Hα emission is an excellent tracer of star formation at z ~ 2 with deviations typically lower than 0.3 dex for individual galaxies. We find that the slope and zero-point of the HAE main sequence at z ~ 2 strongly depend on the dust-correction method used to recover the SFR, although they are consistent with previous works when similar assumptions are made. [ABSTRACT FROM AUTHOR]

In this paper, we present the third data release (DR3) of the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). We identify likely near-infrared counterparts to submillimetre sources in the South Galactic Pole (SGP) field using the VISTA VIKING survey. We search for the most probable counterparts within 15 arcsec of each Herschel source using a probability measure based on the ratio between the likelihood the true counterpart is found close to the submillimetre source and the likelihood that an unrelated object is found in the same location. For 110 374 (57.0 per cent) sources, we find galaxies on the near-infrared images where the probability that the galaxy is associated to the source is greater than 0.8. We estimate the false identification rate to be 4.8 per cent, with a probability that the source has an associated counterpart on the VIKING images of 0.835 ± 0.009. We investigate the effects of gravitational lensing and present 41 (0.14 deg−2) candidate lensed systems with observed flux densities >100 mJy at 500 μm. We include in the data release a probability that each source is gravitationally lensed and discover an additional 5923 sources below 100 mJy that have a probability greater than 0.94 of being gravitationally lensed. We estimate that ∼400–1 000 sources have multiple true identifications in VIKING based on the similarity of redshift estimates for multiple counterparts close to a Herschel source. The data described in this paper can be found at the H-ATLAS website. [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]

ABSTRACT We present Herschel-Spectral and Photometric Imaging Receiver (SPIRE) Fourier transform spectrometer (FTS) and radio follow-up observations of two Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS)-detected strongly lensed distant galaxies. In one of the targeted galaxies H-ATLAS J090311.6+003906 (SDP.81), we detect [O iii] 88 μm and [C ii] 158 μm lines at a signal-to-noise ratio of ∼5. We do not have any positive line identification in the other fainter target H-ATLAS J091305.0−005343 (SDP.130). Currently, SDP.81 is the faintest submillimetre galaxy with positive line detections with the FTS, with continuum flux just below 200 mJy in the 200-600 μm wavelength range. The derived redshift of SDP.81 from the two detections is z = 3.043 ± 0.012, in agreement with ground-based CO measurements. This is the first detection by Herschel of the [O iii] 88 μm line in a galaxy at redshift higher than 0.05. Comparing the observed lines and line ratios with a grid of photodissociation region (PDR) models with different physical conditions, we derive the PDR cloud density n ≈ 2000 cm−3 and the far-ultraviolet ionizing radiation field G0≈ 200 (in units of the Habing field - the local Galactic interstellar radiation field of 1.6 × 10−6 W m−2). Using the CO-derived molecular mass and the PDR properties, we estimate the effective radius of the emitting region to be 500-700 pc. These characteristics are typical for star-forming, high-redshift galaxies. The radio observations indicate that SDP.81 deviates significantly from the local far-infrared/radio (FIR/radio) correlation, which hints that some fraction of the radio emission is coming from an active galactic nucleus (AGN). The constraints on the source size from millimetre-wave observations put a very conservative upper limit of the possible AGN contribution to less than 33 per cent. These indications, together with the high [O iii]/FIR ratio and the upper limit of [O i] 63 μm/[C ii] 158 μm, suggest that some fraction of the ionizing radiation is likely to originate from the AGN. [ABSTRACT FROM AUTHOR]

We investigate whether strong molecular and atomic emission lines at far-infrared wavelengths can influence the identification and derived properties of galaxies selected from broad-band, far-infrared or submillimetre observations. Several of these lines, for example, [C ] 158 m, have been found to be very bright in some galaxies, with fluxes of ≳0.1-1 per cent of the total far-infrared luminosity, and may be even brighter in certain populations at high redshifts. At redshifts where these lines fall in instrument passbands, they can significantly increase the broad-band flux measurements. We estimate that the contributions from line emission could boost the apparent broad-band flux by ≳20-40 per cent in the Herschel and SCUBA-2 bands. Combined with the steep source counts in the submillimetre and far-infrared bands, line contamination has potentially significant consequences for the properties of sources detected in flux-limited continuum surveys, biasing the derived redshift distributions and bolometric luminosities. Indeed, it is possible that some z > 4 sources found in 850-m surveys are being identified in part due to the line contamination from strong [C ] emission. These biases may be even stronger for less-luminous and lower metallicity populations at high redshifts, which are observable with the ALMA and which may have even stronger line-to-continuum ratios. [ABSTRACT FROM AUTHOR]

ABSTRACT We investigate the far-infrared-radio correlation (FRC) of stellar-mass-selected galaxies in the Extended Chandra Deep Field-South using far-infrared (FIR) imaging from Spitzer and radio imaging from the Very Large Array and Giant Metre-Wave Radio Telescope. We stack in redshift bins to probe galaxies below the noise and confusion limits. Radio fluxes are K-corrected using observed flux ratios, leading to tentative evidence for an evolution in spectral index. We compare spectral energy distribution (SED) templates of local galaxies for K-correcting FIR fluxes and show that the data are best fitted by a quiescent spiral template (M51) rather than a warm starburst (M82) or ultra-luminous infrared galaxy (Arp 220), implying a predominance of cold dust in massive galaxies at high redshift. In contrast, we measure total infrared luminosities that are consistent with high star-formation rates. We observe that the FRC index ( q) does not evolve significantly over z= 0-2 when computed from K-corrected 24- or 160-μm photometry, but that using 70-μm fluxes leads to an apparent decline in q beyond z∼ 1. This suggests some change in the SED at high redshift, either a steepening of the spectrum at rest-frame ∼25-35 μm or a deficiency at ∼70 μm leading to a drop in the total infrared-radio ratios. We compare our results to other work in the literature and find synergies with recent findings on the high-redshift FRC, high specific star formation rates of massive galaxies and the cold dust temperatures in these galaxies. [ABSTRACT FROM AUTHOR]

We present first results of a study of the submillimetre (submm) (rest-frame far-infrared) properties of Lyman break galaxies (LBGs) and their lower redshift counterparts BX/BM galaxies, based on Herschel-SPIRE observations of the Northern field of the Great Observatories Origins Deep Survey (GOODS-N). We use stacking analysis to determine the properties of LBGs well below the current limit of the survey. Although LBGs are not detected individually, stacking the infrared luminous LBGs (those detected with Spitzer at 24 m) yields a statistically significant submm detection with mean flux mJy confirming the power of SPIRE in detecting UV-selected high-redshift galaxies at submm wavelengths. In comparison, the Spitzer 24 m detected BX/BM galaxies appear fainter with a stacked value of mJy. By fitting the spectral energy distributions (SEDs) we derive median infrared luminosities, , of 2.8 × 10 L and 1.5 × 10 L for LBGs and BX/BMs, respectively. We find that estimates derived from present measurements are in good agreement with those based on UV data for BX/BM galaxies, unlike the case for infrared luminous LBGs where the UV underestimates the true . Although sample selection effects may influence this result we suggest that differences in physical properties (such as morphologies, dust distribution and extent of star-forming regions) between LBGs and BX/BMs may also play a significant role. [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]

Whether or not supernovae contribute significantly to the overall dust budget is a controversial subject. Submillimetre (sub-mm) observations, sensitive to cold dust, have shown an excess at 450 and 850 μm in young remnants Cassiopeia A (Cas A) and Kepler. Some of the sub-mm emission from Cas A has been shown to be contaminated by unrelated material along the line of sight. In this paper, we explore the emission from material towards Kepler using sub-mm continuum imaging and spectroscopic observations of atomic and molecular gas, via H i, 12CO( J= 2–1) and 13CO( J= 2–1). We detect weak CO emission (peak = 0.2–1 K, 1–2 km s−1 full width at half-maximum) from diffuse, optically thin gas at the locations of some of the sub-mm clumps. The contribution to the sub-mm emission from foreground molecular and atomic clouds is negligible. The revised dust mass for Kepler's remnant is , about half of the quoted values in the original study by Morgan et al., but still sufficient to explain the origin of dust at high redshifts. [ABSTRACT FROM AUTHOR]

If Type II supernovae – the evolutionary end points of short-lived, massive stars – produce a significant quantity of dust then they can explain the rest-frame far-infrared emission seen in galaxies and quasars in the first Gyr of the Universe. Submillimetre (submm) observations of the Galactic supernova remnant, Cas A, provided the first observational evidence for the formation of significant quantities of dust in Type II supernovae. In this paper, we present new data which show that the submm emission from Cas A is polarized at a level significantly higher than that of its synchrotron emission. The orientation is consistent with that of the magnetic field in Cas A, implying that the polarized submm emission is associated with the remnant. No known mechanism would vary the synchrotron polarization in this way and so we attribute the excess polarized submm flux to cold dust within the remnant, providing fresh evidence that cosmic dust can form rapidly. This is supported by the presence of both polarized and unpolarized dust emission in the north of the remnant where there is no contamination from foreground molecular clouds. The inferred dust polarization fraction is unprecedented which, coupled with the brief time-scale available for grain alignment (<300 yr), suggests that supernova dust differs from that seen in other Galactic sources (where per cent) or that a highly efficient grain alignment process must operate in the environment of a supernova remnant. [ABSTRACT FROM AUTHOR]

We present deep 350- and 1200-μm imaging of the region around 4C 41.17 – one of the most-distant and luminous known radio galaxies – obtained with the Submillimeter High Angular Resolution Camera (SHARC-II) and the Max Planck Millimeter Bolometer Array (MAMBO). The radio galaxy is robustly detected at 350 and 1200 μm, as are two nearby 850-μm-selected galaxies; a third 850-μm source is detected at 350 μm and coincides with a ∼2σ feature in the 1200-μm map. Farther away from the radio galaxy additional nine sources are detected at 1200 μm, bringing the total number of detected (sub)millimetre-selected galaxies (SMGs) in this field to 14. Using radio images from the Very Large Array and Spitzer mid-infrared data, we find statistically robust radio and/or 24-μm counterparts to eight out of the 14 SMGs in the field around 4C 41.17. Follow-up spectroscopy with Keck/Low-Resolution and Imaging Spectrograph (LRIS) has yielded redshifts for three out of the eight robustly identified SMGs, placing them in the redshift range that is well below that of 4C 41.17. We infer photometric redshifts for a further four sources using their 1.6-μm (rest-frame) stellar feature as probed by the IRAC bands; only one of them is likely to be at the same redshift as 4C 41.17. Thus at least four, and as many as seven, of the SMGs within the 4C 41.17 field are physically unrelated to the radio galaxy. With the redshift information at hand, we are able to constrain the observed overdensities of SMGs within radial bins stretching to and 100 arcsec (∼0.4 and ∼0.8 Mpc at ) from the radio galaxy to approximately five times and two times that of the field, dropping off to the background value at . We thus confirm that 4C 41.17 resides in an overdense region of the Universe, but we have only been able to identify SMGs along the line of sight to the radio galaxy, typical of the blank-field SMG population. Finally, we report on the discovery of an extremely extended (∼110 kpc) Lyα blob at associated with the brightest 1200-μm source in the field. [ABSTRACT FROM AUTHOR]

We present an analysis of the submillimetre/X-ray properties of 19 X-ray absorbed, Compton-thin quasi-stellar objects (QSOs) selected to have luminosities and redshifts that represent the peak of cosmic QSO activity, i.e.objects at. Of these, we present new data for 11 objects not previously observed at submillimetre wavelengths and additional data for a further three. The detection rate is 42 per cent, much higher than typically reported for samples of QSOs. Detection statistics show (at the 3–4σ level) that this sample of absorbed QSOs has a higher submillimetre output than a matched sample of unabsorbed QSOs. We argue that the far-infrared luminosity is produced by massive star formation. In this case, the correlation found between far-infrared luminosity and redshift can be interpreted as cosmological evolution of the star formation rate in the QSO host galaxies. Because the submillimetre luminous phase is confined to, the high star formation rates are consistent with a scenario in which the QSOs evolve to become local luminous elliptical galaxies.Combining these results with previously published data for X-ray unabsorbed QSOs and submillimetre-selected galaxies, we propose the following evolutionary sequence:(i)the forming galaxy is initially far-infrared luminous but X-ray weak similar to the sources discovered by the Submillimetre Common-User Bolometer Array (SCUBA);(ii)as the black hole and spheroid grow with time, a point is reached when the central QSO becomes powerful enough to terminate the star formation and eject the bulk of the fuel supply (the Compton-thin absorbed QSO phase);(iii)this transition is followed by a period of unobscured QSO activity, which subsequently declines to leave a quiescent spheroidal galaxy. [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]

ABSTRACT We present optical and near-infrared (near-IR) spectroscopy of a z= 2.38 hyperluminous IR galaxy, covering the rest-frame wavelength range from 1000–5000 Å. It appears to comprise two components separated by less than 1 arcsec on the sky (&lsim;8 kpc); one component (B) is blue, the other (P) is red in rest-frame ultraviolet(UV)–optical colours. The combined system has a rest-frame luminosity of ∼8L*[sub V] and its rest-frame optical spectrum is characteristic of a Seyfert active galactic nucleus. However, its rest-frame UV spectrum exhibits striking features associated with young stars, including P-Cygni lines from stellar winds and blueshifted interstellar absorption lines indicative of a galactic outflow. Redshifts are derived from stellar photospheric lines in the UV and from narrow emission lines in the rest-frame optical, and these are compared to those measured for the molecular gas recently detected with the Institut de Radioastronomie Millimetrique (IRAM) interferometer. The offsets indicate that the far-IR emission is most likely associated with the near-IR source P, which hosts the Seyfert nucleus, while the UV-bright component B is blueshifted by 400 km s[sup -1]. This suggests that the two components are probably merging and the resulting gravitational interactions have triggered the hyperluminous activity. Modelling of the UV spectral features implies that the starburst within the UV component of this system has been going on for at least ∼10 Myr. Assuming that the bolometrically-dominant obscured component has a similar lifetime, we estimate that it has so far formed a total stellar mass of ∼10[sup 11] M[sub ⊙] . If this star formation continues at its present level for substantially longer, or if this activity is repeated, then the present-day descendant of N2 850.4 will be a very luminous galaxy. [ABSTRACT FROM AUTHOR]

ABSTRACT We report on the X-ray, optical, near-infrared, submillimetre and radio properties of five extremely red objects (EROs) selected at X-ray wavelengths by XMM-Newton in the Lockman Hole field. They all have enough counts in the X-ray band to allow spectral fitting: four are most probably obscured, Compton-thin active galactic nuclei (AGNs) with redshift-dependent absorbing column densities of 10[sup 22]–10[sup 24] cm[sup -2], whilst the fifth is best fitted by a thermal spectrum and is likely to be a massive elliptical galaxy in a deep gravitational potential. Their optical/near-infrared colours and sizes suggest that X-ray selected EROs comprise a mixture of dusty ‘starburst’ galaxies and non-dusty galaxies that are dominated by either starlight or light from an active nucleus. The colour diagnostics are supported by the submillimetre and radio data; the two AGNs with ‘starburst’ colours have submillimetre or radio flux densities that imply large star formation rates, whilst those with ‘elliptical’ colours do not. The one source detected in the submillimetre waveband has narrow emission lines at a redshift of 1.45. Although the bulk of its radio emission originates from processes other than star formation, it is most probably a radio-quiet ultraluminous infrared galaxy. [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 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 have used ALMA and NOEMA to study the molecular gas reservoirs in 61 ALMA-identified submillimetre galaxies (SMGs) in the COSMOS, UDS, and ECDFS fields. We detect 12CO (⁠|$J_{\rm up} =$| 2–5) emission lines in 50 sources, and [C  i ](3P1 − 3P0) emission in eight, at |$z =$| 1.2–4.8 and with a median redshift of 2.9 ± 0.2. By supplementing our data with literature sources, we construct a statistical CO spectral line energy distribution and find that the 12CO line luminosities in SMGs peak at J up ∼ 6, consistent with similar studies. We also test the correlations of the CO, [C  i ], and dust as tracers of the gas mass, finding the three to correlate well, although the CO and dust mass as estimated from the 3-mm continuum are preferable. We estimate that SMGs lie mostly on or just above the star-forming main sequence, with a median gas depletion timescale, t dep = M gas/SFR, of 210 ± 40 Myr for our sample. Additionally, t dep declines with redshift across z  ∼ 1–5, while the molecular gas fraction, μgas = M gas/ M *, increases across the same redshift range. Finally, we demonstrate that the distribution of total baryonic mass and dynamical line width, M baryon–σ, for our SMGs is consistent with that followed by early-type galaxies in the Coma cluster, providing strong support to the suggestion that SMGs are progenitors of massive local spheroidal galaxies. On the basis of this, we suggest that the SMG populations above and below an 870- μ m flux limit of S 870 ∼ 5 mJy may correspond to the division between slow and fast rotators seen in local early-type galaxies. [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]