Search

We examine the rest-frame far-infrared emission from powerful radio sources with 1.4-GHz luminosity densities of 25 ≤ log(L1.4/W Hz−1) ≤ 26.5 in the extragalactic Spitzer First Look Survey field. We combine Herschel/SPIRE flux densities with Spitzer/Infrared Array Camera and Multiband Imaging Photometer for Spitzer infrared data to obtain total (m) infrared luminosities for these radio sources. We separate our sources into a moderate, 0.4

We analyze subarcsecond resolution interferometric CO line data for 12 submillimeter-luminous (S_(850 μm) ≥ 5 mJy) galaxies with redshifts between 1 and 3, presenting new data for 4 of them. Morphologically and kinematically, most of the 12 systems appear to be major mergers. Five of them are well-resolved binary systems, and seven are compact or poorly resolved. Of the four binary systems for which mass measurements for both separate components can be made, all have mass ratios of 1:3 or closer. Furthermore, comparison of the ratio of compact to binary systems with that observed in local ULIRGs indicates that at least a significant fraction of the compact submillimeter-luminous galaxies (SMGs) must also be late-stage mergers. In addition, the dynamical and gas masses we derive are most consistent with the lower end of the range of stellar masses published for these systems, favoring cosmological models in which SMGs result from mergers. These results all point to the same conclusion that most of the bright SMGs with L_(IR) ≳ 5 × 10^(12) L_☉ are likely major mergers.

Dusty, star forming galaxies contribute to a bright, currently unresolved cosmic far-infrared background. Deep Herschel-SPIRE images designed to detect and characterize the galaxies that comprise this background are highly confused, such that the bulk lies below the classical confusion limit. We analyze three fields from the HerMES programme in all three SPIRE bands (250, 350, and 500 microns); parameterized galaxy number count models are derived to a depth of ~2 mJy/beam, approximately 4 times the depth of previous analyses at these wavelengths, using a P(D) (probability of deflection) approach for comparison to theoretical number count models. Our fits account for 64, 60, and 43 per cent of the far-infrared background in the three bands. The number counts are consistent with those based on individually detected SPIRE sources, but generally inconsistent with most galaxy number counts models, which generically overpredict the number of bright galaxies and are not as steep as the P(D)-derived number counts. Clear evidence is found for a break in the slope of the differential number counts at low flux densities. Systematic effects in the P(D) analysis are explored. We find that the effects of clustering have a small impact on the data, and the largest identified systematic error arises from uncertainties in the SPIRE beam.

Using Herschel Photodetector Array Camera (PACS) and Spectral and Photometric Imaging Receiver (SPIRE) observations of Lockman Hole-North and Great Observatories Origins Deep Survey-North (GOODS-N) as part of the Herschel Multi-tiered Extragalactic Survey (HerMES) project, we explore the far-infrared (IR) properties of a sample of mid-IR-selected starburst-dominated ultraluminous infrared galaxies (ULIRGs) at z∼ 2. The selection of the sample is based on the detection of the stellar bump that appears in the spectral energy distribution of star-forming galaxies at 1.6 μm. We derive robust estimates of infrared luminosities (LIR) and dust temperatures (Td) of the population and find that while the luminosities in our sample span less than an order of magnitude (12.24 ≤ log(LIR/L⊙) ≤ 12.94), they cover a wide range of dust temperatures (25 ≤Td≤ 62 K). Galaxies in our sample range from those that are as cold as high-z submillimetre galaxies (SMGs) to those that are as warm as optically faint radio galaxies (OFRGs) and local ULIRGs. Nevertheless, our sample has median Td= 42.3 K, filling the gap between SMGs and OFRGs, bridging the two populations. We demonstrate that a significant fraction of our sample would be missed from ground-based (sub)mm surveys (850–1200 μm), showing that the latter introduce a bias towards the detection of colder sources. We conclude that Herschel observations confirm the existence of high-z ULIRGs warmer than SMGs, show that the mid-IR selection of high-z ULIRGs is not Td dependent, reveal a large dispersion in Td of high-z ULIRGs and provide the means to characterize the bulk of the ULIRG population, free from selection biases introduced by ground-based (sub)mm surveys.

We describe the production and verification of sky maps of the five SPIRE fields observed as part of the Herschel Multi-tiered Extragalactic Survey (HerMES) during the Science Demonstration Phase (SDP) of the Herschel mission. We have implemented an iterative map-making algorithm (SHIM; The SPIRE-HerMES Iterative Mapper) to produce high fidelity maps that preserve extended diffuse emission on the sky while exploiting the repeated observations of the same region of the sky with many detectors in multiple scan directions to minimize residual instrument noise. We specify here the SHIM algorithm and outline the various tests that were performed to determine and characterize the quality of the maps and verify that the astrometry, point source flux and power on all relevant angular scales meets the needs of the HerMES science goals. These include multiple jackknife tests, determination of the map transfer function and detailed examination of the power spectra of both sky and jackknife maps. The map transfer function is approximately unity on scales from one arcminute to one degree. Final maps (v1.0), including multiple jackknives, as well as the SHIM pipeline, have been used by the HerMES team for the production of SDP papers.

The Spectral and Photometric Imaging Receiver (SPIRE) on Herschel has been carrying out deep extragalactic surveys, one of whose aims is to establish spectral energy distributions (SED)s of individual galaxies spanning the infrared/submillimeter (IR/SMM) wavelength region. We report observations of the (IR/SMM) emission from the Lockman North field (LN) and Great Observatories Origins Deep Survey field North (GOODS-N). Because galaxy images in the wavelength range covered by Herschel generally represent a blend with contributions from neighboring galaxies, we present sets of galaxies in each field especially free of blending at 250, 350, and 500 microns. We identify the cumulative emission of these galaxies and the fraction of the far infrared cosmic background radiation they contribute. Our surveys reveal a number of highly luminous galaxies at redshift z ~< 3 and a novel relationship between infrared and visible emission that shows a dependence on luminosity and redshift.

We study the dust properties of galaxies in the redshift range 0.1 0.5 with L_IR>5x10^{10} L_\odot, appears to be 2-5 K colder than that of AKARI-selected local galaxies with similar luminosities; and the dispersion in T_dust for high-z galaxies increases with L_IR due to the existence of cold galaxies that are not seen among local galaxies. We show that this large dispersion of the L_IR-T_dust relation can bridge the gap between local star-forming galaxies and high-z submillimeter galaxies (SMGs). We also find that three SMGs with very low T_dust (

We present the cross-identification and source photometry techniques used to process Herschel SPIRE imaging taken as part of the Herschel Multi-Tiered Extragalactic Survey (HerMES). Cross-identifications are performed in map-space so as to minimise source blending effects. We make use of a combination of linear inversion and model selection techniques to produce reliable cross-identification catalogues based on Spitzer MIPS 24 micron source positions. Testing on simulations and real Herschel observations show that this approach gives robust results for even the faintest sources S250~10 mJy. We apply our new technique to HerMES SPIRE observations taken as part of the science demostration phase of Herschel. For our real SPIRE observations we show that, for bright unconfused sources, our flux density estimates are in good agreement with those produced via more traditional point source detection methods (SussExtractor; Savage & Oliver et al. 2006) by Smith et al. 2010. When compared to the measured number density of sources in the SPIRE bands, we show that our method allows the recovery of a larger fraction of faint sources than these traditional methods. However this completeness is heavily dependant on the relative depth of the existing 24 micron catalogues and SPIRE imaging. Using our deepest multi-wavelength dataset in GOODS-N, we estimate that the use of shallow 24 micron in our other fields introduces an incompleteness at faint levels of between 20-40 per cent at 250 micron.

The reliability of infrared (IR) and ultraviolet (UV) emissions to measure star formation rates in galaxies is investigated for a large sample of galaxies observed with the SPIRE and PACS instruments on Herschel as part of the HerMES project. We build flux-limited 250 micron samples of sources at redshift z 10 ^{11} L_sun and 0.5< z

We present the first spectroscopic analysis of the faint M31 satellite galaxies, AndXI and AndXIII, and a reanalysis of existing spectroscopic data for two further faint companions, And IX and AndXII. By combining data obtained using the DEIMOS spectrograph mounted on the Keck II telescope with deep photometry from the Suprime-Cam instrument on Subaru, we have calculated global properties for the dwarfs, such as systemic velocities, metallicites and half-light radii.We find each dwarf to be very metal poor ([Fe/H] -2 both photometrically and spectroscopically, from their stacked spectrum), and as such, they continue to follow the luminosity-metallicity relationship established with brighter dwarfs. We are unable to resolve a dispersion for And XI due to small sample size and low S/N, but we set a one sigma upper limit of sigma-v

We present ultra-deep mid-IR spectra of 48 infrared-luminous galaxies in the GOODS-South field obtained with the InfraRed Spectrograph (IRS) on the Spitzer Space Telescope. These galaxies are selected among faint infrared sources (0.14 - 0.5 mJy at 24 um) in two redshift bins (0.76-1.05 and 1.75-2.4) to sample the major contributors to the cosmic infrared background at the most active epochs. We estimate redshifts for 92% of the sample using PAH and Si absorption features. Only few of these galaxies (5% at z~1 and 12% at z~2) have their total infrared luminosity dominated by emission from AGN. The averaged mid-IR spectra of the z~1 LIRGs and of the z~2 ULIRGs are very similar to the averaged spectrum of local starbursts and HII-like ULIRGs, respectively. We find that 6.2um PAH equivalent widths reach a plateau of ~1 um for L(24 mu) < 1E11 L(sun). At higher luminosities, EW (6.2 mu) anti-correlates with L(24 um). Intriguingly, high-z ULIRGs and SMG lie above the local EW (6.2 um) - L(24 um) relationship suggesting that, at a given luminosity, high-z ULIRGs have AGN contributions to their dust emission lower than those of local counterparts. A quantitative analysis of their morphology shows that most of the luminous IR galaxies have morphologies similar to those of IR-quiet galaxies at the same redshift. All z~2 ULIRGs of our sample are IR-excess BzK galaxies and most of them have L(FIR)/L(1600A) ratios higher than those of starburst galaxies at a given UV slope. The ``IR excess'' (Daddi et al. 2007) is mostly due to strong 7.7 um PAH emission and under-estimation of UV dust extinction. On the basis of the AGN-powered L (6 um) continuum measured directly from the mid-IR spectra, we estimate an average intrinsic X-ray AGN luminosity of L(2-10 keV) = (0.1 +/- 0.6) 1E43 erg/s, a value substantially lower than the prediction by Daddi et al. (2007).

In the context of the VLA-COSMOS Deep project additional VLA A array observations at 1.4 GHz were obtained for the central degree of the COSMOS field and combined with the existing data from the VLA-COSMOS Large project. A newly constructed Deep mosaic with a resolution of 2.5" was used to search for sources down to 4 sigma with 1 sigma ~ 12 microJy/beam in the central 50'x50'. This new catalog is combined with the catalog from the Large project (obtained at 1.5"x1.4" resolution) to construct a new Joint catalog. All sources listed in the new Joint catalog have peak flux densities of >5 sigma at 1.5" and/or 2.5" resolution to account for the fact that a significant fraction of sources at these low flux levels are expected to be slighty resolved at 1.5" resolution. All properties listed in the Joint catalog such as peak flux density, integrated flux density and source size are determined in the 2.5" resolution Deep image. In addition, the Joint catalog contains 43 newly identified multi-component sources., 34 pages, 20 figures (3 at reduced resolution). Accepted for publication in ApJS.

Using the IRAM Plateau-de-Bure Interferometer (PdBI) we have searched for the upper fine structure line of neutral carbon (CI(2->1), nu_rest = 809 GHz) and 12CO(J=7->6) (nu_rest=806GHz) towards the submillimetre galaxies (SMGs) GN20 (SMM J123711.9+622212, z = 4.055) and GN20.2 (SMM J123708.8+622202, z = 4.051). The far-infrared (FIR) continuum is detected at 8sigma significance in GN20, with a flux density of S_1.8mm = 1.9+-0.2mJy, while no continuum is detected in GN20.2. Both sources are statistically undetected in both CI and CO(7-6) lines; we derive line luminosity limits for both CI and CO of L', Comment: 7 pages, 3 figures; accepted for publication in MNRAS

Ultra-luminous infrared galaxies (LIR > 1012L⊙) are locally rare, but appear to dominate the co-moving energy density at higher redshifts (z > 2). Many of these are optically faint, dust-obscured galaxies that have been identified by the detection of their thermal dust emission in the sub-mm. Multi-wavelength spectroscopic follow-up observations of these sub-mm galaxies (SMGs) have shown that they are massive (Mstellar ~ 1011M⊙) objects undergoing intense star-formation (SFRs ~ 102–103M⊙ yr−1) with a mean redshift of z ~ 2, coinciding with the epoch of peak quasar activity. Furthermore, the presence of AGNs in ~ 28–50% of SMGs has been unveiled in the X-ray and near-IR. When both AGN and star-formation activity are present, long-slit spectroscopic techniques face difficulties in disentangling their independent contributions from integrated spectra. We have observed Hα emission from a sample of three SMGs in the redshift range z ~ 1.4–2.4 with the integral field spectrograph OSIRIS on Keck, in conjunction with Laser Guide Star Adaptive Optics. The spatially resolved, two-dimensional spectroscopic insight that these observations provide is the only viable probe of the spatial distribution and line-of-sight motion of ionized gas within these galaxies. We detect multiple galactic-scale sub-components, distinguishing the compact, broad Hα emission arising from an AGN from the more extended narrow-line emission of star-forming regions spreading over ~ 8–17 kpc. We explore the dynamics of gas in the inner galaxy halo to improve our understanding of the internal dynamics of this enigmatic galaxy population. We find no evidence of ordered orbital motion such as would be found in a gaseous disk, but rather large velocity offsets of a few hundred kilometers per second between distinct galactic-scale sub-components. Considering the disturbed morphology of SMGs, these sub-components are likely remnants of originally independent gas-rich galaxies that are in the process of merging, hence triggering the ultraluminous SMG phase.

We present the results of a 400ks Chandra survey of 29 extended Ly-alpha emitting nebulae (Ly-alpha Blobs, LABs) in the z=3.09 proto-cluster in the SSA22 field. We detect luminous X-ray counterparts in five LABs, implying a large fraction of active galactic nuclei (AGN) in LABs, f_AGN = 17% down to L_2-32keV ~ 10^44 erg/s. All of the AGN appear to be heavily obscured, with spectral indices implying obscuring column densities of N_H > 10^23 cm^-2. The AGN fraction should be considered a lower limit, since several more LABs not detected with Chandra show AGN signatures in their mid-infrared emission. We show that the UV luminosities of the AGN are easily capable of powering the extended Ly-alpha emission via photo-ionization alone. When combined with the UV flux from a starburst component, and energy deposited by mechanical feedback, we demonstrate that 'heating' by a central source, rather than gravitational cooling is the most likely power source of LABs. We argue that all LABs could be powered in this manner, but that the luminous host galaxies are often just below the sensitivity limits of current instrumentation, or are heavily obscured. No individual LABs show evidence for extended X-ray emission, and a stack equivalent to a >9Ms exposure of an average LAB also yields no statistical detection of a diffuse X-ray component. The resulting diffuse X-ray/Ly-alpha luminosity limit implies there is no hot (T>10^7 K) gas component in these halos, and also rules out inverse Compton scattering of cosmic microwave background photons, or local far-infrared photons, as a viable power source for LABs., 9 pages, 4 figures. Accepted for publication in the Astrophysical Journal. This version updated to accepted version

We present Spitzer-IRAC and MIPS mid-IR observations of a sample of 73 radio-detected submillimeter-selected galaxies (SMGs) with spectroscopic redshifts, the largest such sample published to date. From our data, we find that IRAC colors of SMGs are much more uniform as compared with rest-frame UV and optical colors, and z>1.5 SMGs tend to be redder in their mid-IR colors than both field galaxies and lower-z SMGs. However, the IRAC colors of the SMGs overlap those of field galaxies sufficiently that color-magnitude and color-color selection criteria suggested in the literature to identify SMG counterparts produce ambiguous counterparts within an 8" radius in 20%-35% of cases. We use a rest-frame J–H versus H–K color-color diagram and a S _(24)/S_(8.0) versus S_(8.0)/S_(4.5) color-color diagram to determine that 13%-19% of our sample are likely to contain active galactic nuclei which dominate their mid-IR emission. We observe in the rest-frame JHK colors of our sample that the rest-frame near-IR emission of SMGs does not resemble that of the compact nuclear starburst observed in local ultraluminous IR galaxies and is consistent with more widely distributed star formation. We take advantage of the fact that many high-z galaxy populations selected at different wavelengths are detected by Spitzer to carry out a brief comparison of mid-IR properties of SMGs to UV-selected high-z galaxies, 24 μm-selected galaxies, and high-z radio galaxies, and find that SMGs have mid-IR fluxes and colors which are consistent with being more massive and more reddened than UV-selected galaxies, while the IRAC colors of SMGs are most similar to powerful high-z radio galaxies.

We used the Spitzer Infrared Spectrograph (IRS) to study the mid-IR properties and investigate the energetics of 24 Submillimeter Galaxies (SMGs). This is the largest sample of SMGs observed with Spitzer IRS and covers the full extent of properties of the radio-identified population of SMGs in the redshift range of z ~ 0.65-3.2. We observe broad emission features from Polycyclic Aromatic Hydrocarbons (PAHs) in more than 80% of our sample. We find that the median mid-IR spectrum is well described by a starburst component with an additional power law, Fnu ~ nu^-2, likely representing a < 32% AGN contribution to the bolometric luminosity. Our results thus confirm that starburst activity dominates the bolometric luminosity in SMGs. We find that SMGs show weaker silicate absorption at 9.7um than local ULIRGs. We also find stronger 6.2um PAH emission in SMGs (relative to the 7.7um PAH feature) than in local nuclear starbursts, which may be attributed to lower extinction by ice along the line of sight to SMGs. This suggests that the continuum and PAH emitting regions of SMGs are less obscured than in local starbursts and similarly luminous low-redshift ULIRGs. We interpret these results as evidence for a more extended distribution of cool and warm dust in SMGs compared to the more compact emitting regions in local ULIRGs and starbursts. Together these results suggest that SMGs are not simple high-redshift analogs of local ULIRGs or nuclear starbursts, but instead they appear to have star formation which resembles that seen in less-extreme star-forming environments at z~0 -- suggesting their intense activity is distributed across a far larger region than the ~1-kpc nuclear bursts in local ULIRGs., 21 pages, 11 figures, accepted to The Astrophysical Journal

We use the combined GALFORM semi-analytical model of galaxy formation and GRASIL spectrophotometric code to investigate the properties of galaxies selected via their sub-mm emission. Our fiducial model has previously been shown to fit the properties of local ULIRGs, as well as the number counts of faint sub-mm galaxies. Here, we test the model in detail by comparing the SEDs and stellar, dynamical, gas and halo masses of sub-mm galaxies against observational data. We precisely mimic the sub-mm and radio selection function of the observations and show that the predicted far-infrared properties of model galaxies with S_850>5mJy and S_1.4>30uJy are in good agreement with observations. Although the dust emission model does not assume a single dust temperature, the far-infrared SEDs are well described by single component modified black-body spectrum with characteristic temperature 32+/-5K. We also find evidence that the observations may have uncovered evolution in the far-infrared--radio relation in ULIRGs out to z~2. We show that the predicted redshift distribution of sub-mm galaxies provides a reasonable fit to the observational data with a median redshift z=2.0, with the radio-selected subset predicted to make up approximately 75% of the population. However, the predicted K-band and mid-infrared (3--8um) flux densities of the sub-mm galaxies (and LBGs) are up to a factor 10x fainter than observed. This discrepancy may indicate that the stellar masses of the sub-mm galaxies in the model are too low: M~10^10Mo, while observations suggest more massive systems, M~10^11Mo. Finally, we discuss the potential modifications to the models which may improve the fit to the observational data. [Abridged], Accepted for publication in MNRAS

The Spitzer-COSMOS survey (S-COSMOS) is a Legacy program (Cycles 2+3) designed to carry out a uniform deep survey of the full 2 sq deg COSMOS field in all seven Spitzer bands (3.6, 4.5, 5.6, 8.0, 24.0, 70.0, 160.0 u). This paper describes the survey parameters, mapping strategy, data reduction procedures, achieved sensitivities to date, and the complete data set for future reference. We show that the observed infrared backgrounds in the S-COSMOS field are within 10% of the predicted background levels. The fluctuations in the background at 24u have been measured and do not show any significant contribution from cirrus, as expected. In addition, we report on the number of asteroid detections in the low galactic latitude COSMOS field. We use the Cycle 2 S-COSMOS data to determine preliminary number counts, and compare our results with those from previous Spitzer Legacy surveys (e.g. SWIRE, GOODS). The results from this "first analysis" confirm that the S-COSMOS survey will have sufficient sensitivity with IRAC to detect ~ L* disks and spheroids out to z ~ 3, and with MIPS to detect ultraluminous starbursts and AGN out to z ~3 at 24u and out to z ~1.5-2 at 70u and 160u.

We present observations at 1.4 and 250 GHz of the $z\sim 5.7$ Ly$\alpha$ emitters (LAE) in the COSMOS field found by Murayama et al.. At 1.4 GHz there are 99 LAEs in the lower noise regions of the radio field. We do not detect any individual source down to 3$\sigma$ limits of $\sim 30\mu$Jy beam$^{-1}$ at 1.4 GHz, nor do we detect a source in a stacking analysis, to a 2$\sigma$ limit of $2.5\mu$Jy beam$^{-1}$. At 250 GHz we do not detect any of the 10 LAEs that are located within the central regions of the COSMOS field covered by MAMBO ($20' \times 20'$) to a typical 2$\sigma$ limit of $S_{250} 6\times 10^{24}$ W Hz$^{-1}$ in the LAE sample. The radio and millimeter observations also rule out any highly obscured, extreme starbursts in the sample, ie. any galaxies with massive star formation rates $> 1500$ M$_\odot$ year$^{-1}$ in the full sample (based on the radio data), or 500 M$_\odot$ year$^{-1}$ for the 10% of the LAE sample that fall in the central MAMBO field. The stacking analysis implies an upper limit to the mean massive star formation rate of $\sim 100$ M$_\odot$ year$^{-1}$.

The VLA-COSMOS large project is described and its scientific objective is discussed. We present a catalog of ~ 3,600 radio sources found in the 2deg^2 COSMOS field at 1.4 GHz. The observations in the VLA A and C configuration resulted in a resolution of 1.5''x1.4'' and a mean rms noise of ~ 10.5(15) uJy/beam in the central 1(2)deg^2. 80 radio sources are clearly extended consisting of multiple components, and most of them appear to be double-lobed radio galaxies. The astrometry of the catalog has been thoroughly tested and the uncertainty in the relative and absolute astrometry are 130mas and, 49 pages, 18 figures; accepted for publication in the ApJS, COSMOS special issue. The data will be available from the COSMOS archive at IPAC/IRSA http://irsa.ipac.caltech.edu/Missions/cosmos.html, more information on the VLA-COSMOS survey can be found at http://www.mpia-hd.mpg.de/COSMOS/, full version available at http://www.mpia-hd.mpg.de/COSMOS/#paper

We present mid-infrared spectra of 5 submillimeter galaxies at z=0.65-2.38 taken with the Spitzer Space Telescope. Four of these sources, at z, 4 pages, 2 figures; accepted to ApJ Letter, small changes from submitted version

We present Atacama Large Millimeter/submillimeter Array (ALMA) 870 μm (345 GHz) data for 49 high-redshift (0.47 < z < 2.85), luminous 11.7 < log (L_(bol/L_⊙) < 14.2) radio-powerful active galactic nuclei (AGNs), obtained to constrain cool dust emission from starbursts concurrent with highly obscured radiative-mode black hole (BH) accretion in massive galaxies that possess a small radio jet. The sample was selected from the Wide-field Infrared Survey Explorer with extremely steep (red) mid-infrared colors and with compact radio emission from NVSS/FIRST. Twenty-six sources are detected at 870 μm, and we find that the sample has large mid- to far-infrared luminosity ratios, consistent with a dominant and highly obscured quasar. The rest-frame 3 GHz radio powers are 24.7 < log (P_(3.0 GHz)/W Hz^(-1)) and all sources are radio-intermediate or radio-loud. BH mass estimates are 7.7 < log(M_(BH)/M_⊙) < 10.2. The rest-frame 1–5 μm spectral energy distributions are very similar to the "Hot DOGs" (hot dust-obscured galaxies), and steeper (redder) than almost any other known extragalactic sources. ISM masses estimated for the ALMA-detected sources are 9.9 < log (M_(ISM)/M_⊙) < 11.75 assuming a dust temperature of 30 K. The cool dust emission is consistent with star formation rates reaching several thousand M_⊙ yr^(−1), depending on the assumed dust temperature, but we cannot rule out the alternative that the AGN powers all the emission in some cases. Our best constrained source has radiative transfer solutions with approximately equal contributions from an obscured AGN and a young (10–15 Myr) compact starburst.

We report the redshift of an unlensed, highly obscured submillimetre galaxy (SMG), HS1700.850.1, the brightest SMG (S850um =19.1 mJy) detected in the JCMT/SCUBA-2 Baryonic Structure Survey, based on the detection of its CO line emission. Using the IRAM PdBI-WIDEX with 3.6GHz band width, we serendipitously detect an emission line at 150.6 GHz. From a search over 14.5 GHz in the 3-mm and 2-mm atmospheric windows, we confirm the identification of this line as CO(5-4) at z = 2.816, meaning that it does not reside in the z~2.30 proto-cluster in this field. Measurement of the 870um source size (, 9 pages, 6 figures, 3 tables, accepted in MNRAS

We present high-resolution 870-um ALMA continuum maps of 30 bright sub-millimeter sources in the UKIDSS UDS field. These sources are selected from deep, 1-square degrees 850-um maps from the SCUBA--2 Cosmology Legacy Survey, and are representative of the brightest sources in the field (median SCUBA2 flux S_850=8.7+/-0.4 mJy). We detect 52 sub-millimeter galaxies (SMGs) at >4-sigma significance in our 30 ALMA maps. In 61+/-17% of the ALMA maps the single-dish source comprises a blend of >=2 SMGs, where the secondary SMGs are Ultra--Luminous Infrared Galaxies (ULIRGs) with L_IR>10^12 Lo. The brightest SMG contributes on average 80+/-4% of the single-dish flux density, and in the ALMA maps containing >=2 SMGs the secondary SMG contributes 25+/-3% of the integrated ALMA flux. We construct source counts and show that multiplicity boosts the apparent single-dish cumulative counts by 20% at S_870>7.5mJy, and by 60% at S_870>12mJy. We combine our sample with previous ALMA studies of fainter SMGs and show that the counts are well-described by a double power-law with a break at 8.5+/-0.6mJy. The break corresponds to a luminosity of ~6x10^12Lsol or a star-formation rate of ~1000Mo/yr. For the typical sizes of these SMGs, which are resolved in our ALMA data with r=1.2+/-0.1kpc, this yields a limiting SFR density of ~100Msol/yr/kpc2. Finally, the number density of S_870>2mJy SMGs is 80+/-30 times higher than that derived from blank-field counts. An over-abundance of faint SMGs is inconsistent with line-of-sight projections dominating multiplicity in the brightest SMGs, and indicates that a significant proportion of these high-redshift ULIRGs must be physically associated., 14 pages, 6 figures. ApJ in press

We present Early Science observations with the Large Millimeter Telescope, AzTEC 1.1 mm continuum images and wide bandwidth spectra (73-111 GHz) acquired with the Redshift Search Receiver, towards four bright lensed submillimetre galaxies identified through the Herschel Lensing Survey-snapshot and the SCUBA-2 Cluster Snapshot Survey. This pilot project studies the star formation history and the physical properties of the molecular gas and dust content of the highest redshift galaxies identified through the benefits of gravitational magnification. We robustly detect dust continuum emission for the full sample and CO emission lines for three of the targets. We find that one source shows spectroscopic multiplicity and is a blend of three galaxies at different redshifts (z=2.040, 3.252 and 4.680), reminiscent of previous high-resolution imaging follow-up of unlensed submillimetre galaxies, but with a completely different search method, that confirm recent theoretical predictions of physically unassociated blended galaxies. Identifying the detected lines as 12CO (J_up=2-5) we derive spectroscopic redshifts, molecular gas masses, and dust masses from the continuum emission. The mean H_2 gas mass of the full sample is (2.0 +- 0.2) x 10^11 M_sun/\mu, and the mean dust mass is (2.0+-0.2) x 10^9 M_sun/\mu, where \mu=2-5 is the expected lens amplification. Using these independent estimations we infer a gas-to-dust ratio of \delta_GDR=55-75, in agreement with other measurements of submillimetre galaxies. Our magnified high-luminosity galaxies fall on the same locus as other high-redshift submillimetre galaxies, extending the L'_CO - L_FIR correlation observed for local luminous and ultraluminous infrared galaxies to higher FIR and CO luminosities., Comment: Minor changes to match the published version

We present 20 WISE-selected galaxies with bolometric luminosities L_bol > 10^14 L_sun, including five with infrared luminosities L_IR = L(rest 8-1000 micron) > 10^14 L_sun. These "extremely luminous infrared galaxies," or ELIRGs, were discovered using the "W1W2-dropout" selection criteria which requires marginal or non-detections at 3.4 and 4.6 micron (W1 and W2, respectively) but strong detections at 12 and 22 micron in the WISE survey. Their spectral energy distributions are dominated by emission at rest-frame 4-10 micron, suggesting that hot dust with T_d ~ 450K is responsible for the high luminosities. These galaxies are likely powered by highly obscured AGNs, and there is no evidence suggesting these systems are beamed or lensed. We compare this WISE-selected sample with 116 optically selected quasars that reach the same L_bol level, corresponding to the most luminous unobscured quasars in the literature. We find that the rest-frame 5.8 and 7.8 micron luminosities of the WISE-selected ELIRGs can be 30-80% higher than that of the unobscured quasars. The existence of AGNs with L_bol > 10^14 L_sun at z > 3 suggests that these supermassive black holes are born with large mass, or have very rapid mass assembly. For black hole seed masses ~ 10^3 M_sun, either sustained super-Eddington accretion is needed, or the radiative efficiency must be, 17 pages in emulateapj format, including 11 figures and 5 tables. ApJ in press

The WISE mission has unveiled a rare population of high-redshift ($z=1-4.6$), dusty, hyper-luminous galaxies, with infrared luminosities $L_{\rm IR} > 10^{13}~L_{\odot}$, and sometimes exceeding $10^{14}~L_{\odot}$. Previous work has shown that their dust temperatures and overall far-IR SEDs are significantly hotter than expected for star-formation. We present here an analysis of the rest-frame optical through mid-IR SEDs for a large sample of these so-called "Hot, Dust-Obscured Galaxies" (Hot DOGs). We find that the SEDs of Hot DOGs are generally well modeled by the combination of a luminous, yet obscured AGN that dominates the rest-frame emission at $\lambda > 1\mu\rm m$ and the bolometric luminosity output, and a less luminous host galaxy that is responsible for the bulk of the rest optical/UV emission. Even though the stellar mass of the host galaxies may be as large as $10^{11}-10^{12}~M_{\odot}$, the AGN emission, with luminosities comparable to those of the most luminous QSOs known, require that either Hot DOGs have black hole masses significantly in excess of the local relations, or that they radiate significantly above the Eddington limit. We show that, while rare, the number density of Hot DOGs is comparable to that of equally luminous but unobscured (i.e., Type 1) QSOs. This is inconsistent with the trend of a diminishing fraction of obscured objects with increasing luminosity found for less luminous QSOs, possibly indicating a reversal in this relation at high luminosity, and that Hot DOGs are not the torus-obscured counterparts of the known optically selected, largely unobscured Hyper-Luminous QSOs. Hot DOGs may represent a different type of galaxy and thus a new component of the galaxy evolution paradigm. Finally, we discuss the environments of Hot DOGs and show that these objects are in regions as dense as those of known high-redshift proto-clusters.(Abridged), Comment: Accepted for publication in The Astrophysical Journal. Text and figures modified to address referee's comments. 16 pages, 12 figures, 2 tables

We present JCMT SCUBA-2 850microns submillimetre (submm) observations of 30 mid-infrared (mid-IR) luminous AGN, detected jointly by the WISE all-sky IR survey and the NVSS/FIRST radio survey. These rare sources are selected by their extremely red mid-infrared spectral energy distributions (SEDs) and compact radio counterparts. Further investigations show that they are highly obscured, have abundant warm AGN-heated dust and are thought to be experiencing intense AGN feedback. These galaxies appear to be consistent with an AGN-dominated galaxy, and could be a transient phase of merging galaxies. When comparing the number of submm galaxies (SMGs) detected serendipitously in the surrounding 1.5-arcmin to those in blank-field submm surveys, there is a very significant overdensity, of order 5, but no sign of radial clustering centred at our primary objects. The WISE/radio-selected AGN thus reside in 10-Mpc-scale overdense environments, that could be forming in pre-viralised clusters of galaxies. WISE/radio-selected AGNs appear to be the strongest signposts of high-density regions of active, luminous and dusty galaxies. SCUBA-2 850microns observations indicate that their submm fluxes are low compared to many popular AGN SED templates, hence the WISE/radio-selected AGNs have either less cold and/or more warm dust emission than normally assumed for typical AGN. Most of the targets are not detected, only four targets are detected at SCUBA-2 850microns, and have total IR luminosities >= 10^13 L_solar, if their redshifts are consistent with the subset of the 10 SCUBA-2 undetected targets with known redshifts, z ~ 0.44 - 2.86., 17 pages, 4 tables, 11 figures. arXiv admin note: text overlap with arXiv:1406.2506

We present high-resolution (0.3'') ALMA 870um imaging of 52 sub-millimeter galaxies (SMGs) in the Ultra Deep Survey (UDS) field and investigate the size and morphology of the sub-millimeter (sub-mm) emission on 2-10kpc scales. We derive a median intrinsic angular size of FWHM=0.30$\pm$0.04'' for the 23 SMGs in the sample detected at a signal-to-noise ratio (SNR) >10. Using the photometric redshifts of the SMGs we show that this corresponds to a median physical half-light diameter of 2.4$\pm$0.2kpc. A stacking analysis of the SMGs detected at an SNR, 16 pages, 7 figures, accepted for publication in ApJ

We have determined the relation between the AGN luminosities at rest-frame 6 μm associated with the dusty torus emission and at 2–10 keV energies using a complete, X-ray-flux-limited sample of 232 AGN drawn from the Bright Ultra-hard XMM-Newton Survey. The objects have intrinsic X-ray luminosities between 1042 and 1046 erg s−1 and redshifts from 0.05 to 2.8. The rest-frame 6 μm luminosities were computed using data from the Wide-field Infrared Survey Explorer and are based on a spectral energy distribution decomposition into AGN and galaxy emission. The best-fitting relationship for the full sample is consistent with being linear, L6 μm ∝ L0.99±0.032−10keVL2−10keV0.99±0.03, with intrinsic scatter, Δ log L6 μm ∼ 0.35 dex. The L6μm/L2−10keVL6μm/L2−10keV luminosity ratio is largely independent of the line-of-sight X-ray absorption. Assuming a constant X-ray bolometric correction, the fraction of AGN bolometric luminosity reprocessed in the mid-IR decreases weakly, if at all, with the AGN luminosity, a finding at odds with simple receding torus models. Type 2 AGN have redder mid-IR continua at rest-frame wavelengths, SM, FJC, XB, AH-C and AA-H acknowledge funding from the Spanish Ministry of Economy and Competitiveness under grant AYA2012-31447, which is partly funded by the FEDER programme. SM, FJC and AA-H acknowledge financial support from the ARCHES project (7th Framework of the European Union, no. 313146). AA-H acknowledges support from the Universidad de Cantabria through the Augusto G. Linares programme. AC, RDC and PS acknowledge financial support from the Italian Ministry of Education, Universities and Research (PRIN2010-2011, grant no. 2010NHBSBE) and from ASI (grant no. I/088/06/0).

We present two-dimensional spectroscopy covering the rest-frame wavelengths of strong optical emission lines in six luminous submillimetre galaxies (SMGs) at z= 1.3–2.5. Using this near-infrared integral field spectroscopy together with Hubble Space Telescope ACS and NICMOS imaging, we map the dynamics and morphologies of these systems on scales from 4–11 kpc. Four of the systems show multiple components in their spatially resolved spectra with average velocity offsets of ~180 km s^(−1) across 8 kpc in projection. From the ensemble properties of eight galaxies, from our survey and the literature, we estimate the typical dynamical masses of bright SMGs as 5 ± 3 × 10^(11) M_⊙. This is similar to recent estimates of their stellar masses – suggesting that the dynamics of the central regions of these galaxies are baryon dominated, with a substantial fraction of those baryons in stars by the epoch of observation. Combining our dynamical mass estimates with stellar luminosities for this population, we investigate whether SMGs can evolve on to the Faber–Jackson (FJ) relation for local ellipticals. Adopting a typical lifetime of τ_(burst) ~300 Myr for the submillimetre-luminous phase – using the latest estimates of gas masses, star formation rates and active galactic nucleus contribution to the bolometric luminosities – we find that the stellar populations of SMGs should fade to place them on the FJ relation, at M_K ~ −25.1. Furthermore, using the same starburst lifetime we correct the observed space density of SMGs for the duty cycle to derive a volume density of the progenitors of ~1 × 10^(−4) Mpc^(−3). This is consistent with the space density of local luminous early-type galaxies with M_K ~ −25.1, indicating that SMGs can evolve on to the scaling relations observed for local early-type galaxies, and the observed population at z ~ 2 is then sufficient to account for the formation of the whole population of ≳3 L^*_K ellipticals seen at z ~ 0.

We present high resolution 890 micron images of two 20 mJy submillimeter galaxies, SMMJ123711+622212 and MIPS~J142824.0+352619, obtained using the Submillimeter Array (SMA). Using submillimeter interferometric observations with an angular resolution of 2.5", the coordinates of these high redshift sources are determined with an accuracy of 0.2". The new SMA data on SMMJ123711+622212 reveal an unresolved submm source offset to the east by 0.8" from an optical galaxy found in deep HST images, suggesting either a large galaxy with a dusty central region, or an interacting galaxy system. The SMA image of hyper-luminous (LFIR = 3.2 x 10^{13} Lsun) source MIPS~J142824.0+352619 provides a firm upper limit to the source size of < 1.2. This constraint provides evidence that the foreground lens is only weakly affecting the observed high FIR luminosity., 11 pages, 2 figures, ApJL accepted

In this paper we present results from an IRAM Plateau de Bure millimetre-wave Interferometer (PdBI) survey for CO emission towards radio-detected submillimetre galaxies (SMGs) with known optical and near-infrared spectroscopic redshifts. Five sources in the redshift range z~1-3.5 were detected, nearly doubling the number of SMGs detected in CO. We summarise the properties of all 12 CO-detected SMGs, as well as 6 sources not detected in CO by our survey, and use this sample to explore the bulk physical properties of the SMG population as a whole. The median CO line luminosity of the SMGs is = (3.8 +- 2.0) x 10^10 K km/s pc^2. Using a CO-to-H_2 conversion factor appropriate for starburst galaxies, this corresponds to a molecular gas mass = (3.0 +- 1.6) x 10^10 Msun within a ~2kpc radius, about four times greater than the most luminous local ultraluminous infrared galaxies (ULIRGs) but comparable to that of the most extreme high-redshift radio galaxies and QSOs. The median CO fwhm linewidth is broad, = 780 +- 320 km/s, and the SMGs often have double peaked line profiles, indicative of either a merger or a disk. From their median gas reservoirs (~3 x 10^10 Msun) and star-formation rates (>700 Msun/yr) we estimate a lower limit on the typical gas-depletion time scale of >40Myr in SMGs. This is marginally below the typical age expected for the starbursts in SMGs, and suggests that negative feedback processes may play an important role in prolonging the gas consumption time scale. We find a statistically-significant correlation between the far-infrared and CO luminosities of the SMGs which extends the observed correlation for local ULIRGs to higher luminosities and higher redshifts. [ABRIDGED]

Long-duration gamma-ray bursts (GRBs) accompany the deaths of some massive stars and hence, because massive stars are short-lived, are a tracer of star formation activity. Given that GRBs are bright enough to be seen to very high redshifts and detected even in dusty environments, they should therefore provide a powerful probe of the global star formation history of the Universe. The potential of this approach can be investigated via submillimetre (submm) photometry of GRB host galaxies. Submm luminosity also correlates with star formation rate, so the distribution of host-galaxy submm fluxes should allow us to test the two methods for consistency. Here, we report new JCMT/SCUBA 850-mum measurements for 15 GRB hosts. Combining these data with results from previous studies, we construct a sample of 21 hosts with 4 mJy) galaxies. Furthermore, the optical/infrared properties of the submm-brightest GRB hosts are not typical of the galaxy population selected in submm surveys, although the sample size is still small. Possible selection effects and physical mechanisms which may explain these discrepancies are discussed

We present observations of a remarkable submillimetre-selected galaxy, SMMJ16359+6612. This distant galaxy lies behind the core of a massive cluster of galaxies, A2218, and is gravitationally lensed by the foreground cluster into three discrete images which were identified in deep submillimetre maps of the cluster core at both 450 and 850micron. Subsequent follow-up using deep optical and NIR images identify a faint counterpart to each of the 3 images, with similar red optical--NIR colours and HST morphologies. By exploiting a detailed mass model for the cluster lens we estimate that the combined images of this galaxy are magnified by a factor of ~45, implying that this galaxy would have un-lensed magnitudes K_s=22.9 and I=26.1, and an un-lensed 850micron flux density of only 0.8mJy. Moreover, the highly constrained lens model predicted the redshift of SMMJ16359+6612 to be z=2.6+/-0.4. We confirm this estimate using deep optical and NIR Keck spectroscopy, measuring a redshift of z=2.516. SMMJ16359+6612 is the faintest submm-selected galaxy so far identified with a precise redshift. Thanks to the large gravitational magnification of this source, we identify 3 sub-components in this submm galaxy, which are also seen in the NIRSPEC data, arguing for either a strong dust (lane) absorption or a merger. Interestingly, there are 2 other highly-amplified galaxies at almost identical redshifts in this field (although neither is a strong submm emitter). The 3 galaxies lie within a ~100kpc region on the background sky, suggesting this submm galaxy is located in a dense high-redshift group.

We report IRAM Plateau de Bure, millimeter interferometry of three z=~2.4 to 3.4, SCUBA deep field galaxies. Our CO line observations confirm the rest-frame UV/optical redshifts, thus more than doubling the number of confirmed, published redshifts of the faint submillimeter population and proving their high-z nature. In all three sources our measurements of the intrinsic gas and dynamical mass are large (1e10 to 1e11 Msun). In at least two cases the data show that the submillimeter sources are part of an interacting system. Together with recent information gathered in the X-ray, optical and radio bands our observations support the interpretation that the submm-population consists of gas rich (gas to dynamical mass ratio ~0.5) and massive, composite starburst/AGN systems, which are undergoing a major burst of star formation and are evolving into m*-galaxies.

We present an extended analysis of the SCUBA observations of the Hubble Deep Field (HDF), expanding the areal coverage of the Hughes et al. 1998 study by a factor of ~1.8 and containing at least three further sources in addition to the five in that study. We also announce the public release of the reduced data products. The map is the deepest ever made in the sub-millimetre, obtained in excellent conditions (median 850um optical depth of 0.16). Two independent reductions were made, one with SURF and the other with a wholly algorithmic IDL analysis which we present in detail here. Of the three new sources, all appear to be at z>~0.9 and one is provisionally associated with an Extremely Red Object (I-K>5). There appears to be no significant cross-correlation signal between the 850um fluctuations and sources detected by ISOCAM, the VLA or Chandra, nor with Very Red Objects (I-K>4), nor quasars and quasar candidates in the HDF (notwithstanding a small number of individual weak candidate detections). This is consistent with interpretations where the 850um-selected galaxies are at higher redshifts than those currently probed by ISOCAM/VLA, and predominantly not Compton-thin AGN. There are only one or two compelling cases for the radio source being the sub-mm source. Nevertheless, most SCUBA-HDF point sources have a nearby radio source apparently well-separated from the sub-mm centroid., MNRAS in press; minor revisions. 23 pages, 13 figures. Uses BoxedEPS and mn2e.cls (included). SCUBA-HDF data release at http://astro.ic.ac.uk/elais/scuba_public.html

A cosmologically significant population of very luminous high-redshift galaxies has recently been discovered at submm wavelengths. Advances in submm detector technologies have opened this new window on the distant Universe. Here we discuss the properties of the high-redshift submm galaxies, their significance for our understanding of the process of galaxy formation, and the selection effects that apply to deep submm surveys. The submm galaxies generate a significant fraction of the energy output of all galaxies in the early Universe. We emphasize the importance of studying a complete sample of submm galaxies, and stress that because they are typically very faint in other wavebands, these follow-up observations are very challenging. Finally, we discuss the surveys that will be made using the next generation of submm-wave instruments under development., 86 pages, 23 figures. In press at Physics Reports. Higher-quality version of Figure 1 can be found in astro-ph/9911069. Replaced to match proofs, correct minor typos and update references

Spectroscopic surveys of luminous submillimetre-selected sources have uncoveredoptically-bright galaxies at z

We present the results of a multi-wavelength study of the 19 most significant sub-mm sources detected in the SCUBA 8-mJy survey. As described in Scott et al. (2001), this survey covers ~260 arcmin^2 using the sub-millimetre camera SCUBA, to a limiting source detection limit S(850um) ~ 8 mJy. One advantage of this relatively bright flux-density limit is that accurate astrometric positions are potentially achievable for every source using existing radio and/or mm-wave interferometers. However, an associated advantage is that SED-based redshift constraints should be more powerful than in fainter sub-mm surveys. Here we therefore exploit the parallel SCUBA 450um data, in combination with existing radio and ISO data at longer and shorter wavelengths to set constraints on the redshift of each source. We also analyse new and existing optical and near-infrared imaging of our SCUBA survey fields to select potential identifications consistent with these constraints. Our derived SED-based redshift constraints, and the lack of statistically significant associations with even moderately bright galaxies allow us to conclude that all 19 sources lie at z > 1, and at least half of them apparently lie at z > 2.

We present the source catalogue for the SCUBA Lens Survey. We summarise the results of extensive multi-wavelength observations of the 15 submillimetre-selected galaxies in the catalogue, from X-rays to radio. We discuss the main observational characteristics of faint submillimetre galaxies as a population, and consider their interpretation within the framework of our understanding of galaxy formation and evolution.

The SCUBA-2 Ultra Deep Imaging EAO Survey (STUDIES) is a three-year JCMT Large Program aiming at reaching the 450 $\mu$m confusion limit in the COSMOS-CANDELS region, to study a representative sample of the high-redshift far-infrared galaxy population that gives rise to the bulk of the far-infrared background. We present the first-year data from STUDIES. We have reached a 450 $\mu$m noise level of 0.91~mJy for point sources at the map center, covered an area of 151 arcmin$^2$, and detected 98 and 141 sources at 4.0 and 3.5 $\sigma$, respectively. Our derived counts are best constrained in the 3.5-25 mJy regime using directly detected sources. Below the detection limits, our fluctuation analysis further constrains the slope of the counts down to 1 mJy. The resulting counts at 1-25 mJy are consistent with a power law having a slope of $-2.59$ ($\pm0.10$ for 3.5-25 mJy, and $^{+0.4}_{-0.7}$ for 1-3.5 mJy). There is no evidence of a faint-end termination or turn-over of the counts in this flux density range. Our counts are also consistent with previous SCUBA-2 blank-field and lensing cluster surveys. The integrated surface brightness from our counts down to 1 mJy is $90.0\pm17.2$ Jy deg$^{-2}$, which can account for up to $83^{+15}_{-16}\%$ of the COBE 450 $\mu$m background. We show that Herschel counts at 350 and 500 $\mu$m are significantly higher than our 450 $\mu$m counts, likely caused by its large beam and source clustering. High-angular resolution instruments like SCUBA-2 at 450 $\mu$m are therefore highly beneficial for measuring the luminosity and spatial density of high-redshift dusty galaxies., Comment: ApJ accepted. revised version uploaded

Observations made using COBE, SCUBA, ISO and MAMBO have provided a reasonable working knowledge of both the intensity of the submm and far-infrared background radiation and the source counts of luminous high-redshift dusty galaxies. However, because there are uncertainties in the background intensity determinations, the samples of detected galaxies are small, and most importantly, their redshift distributions are very incomplete, details of the evolution of dusty galaxies remain unresolved. The next steps forward in the field will be the launches of SIRTF and ASTRO-F, the commissioning of SOFIA and new, more capable ground-based mm/submm-wave cameras - BOLOCAM, SHARC-II and SCUBA-II - the use of ultra-long duration balloon experiments, such as BLAST, the construction of ALMA and the arrival of FIRST, and ultimately the advent of space-borne far-infrared interferometers, such as SPECS. There are also exciting prospects for direct mm/submm-wave CO-line redshift surveys using wide-band spectrographs. Using these new facilities, the number of high-redshift dusty galaxies known will be increased dramatically. Spectroscopy using SIRTF, SOFIA and FIRST will probe the astrophysical processes within these sources in detail, hopefully addressing the open question of the fraction of the counts and background radiation that is generated by the formation of high-mass stars and by active galactic nuclei (AGNs). The spatial and spectral structure of distant dusty galaxies will finally be resolved in detail using ALMA and SPECS.

We present HST WFC3 F160W imaging and infrared spectral energy distributions for twelve extremely luminous, obscured AGN at $1.8, Comment: ApJ, accepted. Updated to reflect the accepted version

We present statistically significant detections at 850um of the Lyman Break Galaxy (LBG) population at z=3, 4, and 5 using data from the Submillimetre Common User Bolometer Array 2 (SCUBA-2) Cosmology Legacy Survey (S2CLS) in the United Kingdom Infrared Deep Sky Survey Ultra Deep Survey (UKIDSS-UDS) field. We employ a stacking technique to probe beneath the survey limit to measure the average 850um flux density of LBGs at z=3, 4, and 5 with typical ultraviolet luminosities of L(1700A)~10^29 erg/s/Hz. We measure 850um flux densities of (0.25 +/- 0.03, (0.41 +/- 0.06), and (0.88 +/- 0.23) mJy respectively, and find that they contribute at most 20 per cent to the cosmic far-infrared background at 850um. Fitting an appropriate range of spectral energy distributions to the z=3, 4, and 5 LBG stacked 24-850um fluxes, we derive infrared (IR) luminosities of L(8-1000um)~3.2, 5.5, and 11.0x10^11 Lsun (corresponding to star formation rates of ~50-200 Msun/yr) respectively. We find that the evolution in the IR luminosity density of LBGs is broadly consistent with model predictions for the expected contribution of luminous IR galaxy (LIRG) to ultraluminous IR galaxy (ULIRG) type systems at these epochs. We also see a strong positive correlation between stellar mass and IR luminosity. Our data are consistent with the main sequence of star formation showing little or no evolution from z=3 to 5. We have also confirmed that, for a fixed mass, the reddest LBGs (UV slope Beta -> 0) are indeed redder due to dust extinction, with SFR(IR)/SFR(UV) increasing by approximately an order of magnitude over -2, Comment: 12 pages, 8 figures, submitted to MNRAS

We present Submillimeter Array (SMA) [CII] 158um and Jansky Very Large Array (JVLA) $^{12}$CO(1-0) line emission maps for the bright, lensed, submillimeter source at $z=5.2430$ behind Abell 773: HLSJ091828.6+514223 (HLS0918). We combine these measurements with previously reported line profiles, including multiple $^{12}$CO rotational transitions, [CI], water and [NII], providing some of the best constraints on the properties of the interstellar medium (ISM) in a galaxy at $z>5$. HLS0918 has a total far-infrared (FIR) luminosity L_FIR(8-1000um) = (1.6$\pm$0.1)x10^14 L_sun/mu, where the total magnification mu_total = 8.9$\pm$1.9, via a new lens model from the [CII] 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 which 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, 28 pages, 9 figures, accepted in ApJ

To extend the molecular gas measurements to typical star-forming galaxies (SFGs) with SFR < 40 Msun yr^{-1} and M* < 2.5x10^{10} Msun at z~1.5-3, we have observed CO emission with the IRAM Plateau de Bure Interferometer and 30m telescope for five strongly-lensed galaxies selected from the Herschel Lensing Survey. These observations are combined with a compilation of CO measurements from the literature. We infer the luminosity correction factors r2,1 = 0.81+/-0.20 and r3,1 = 0.57+/-0.15 for the J=2 and J=3 CO transitions, respectively, valid for SFGs at z>1. The combined sample of CO-detected SFGs at z>1 shows a large spread in star formation efficiency (SFE), such that SFE extend beyond the low values of local spirals and overlap the distribution of z>1 sub-mm galaxies. We find that the spread in SFE (or equivalently in molecular gas depletion timescale) is due to primarily the specific star formation rate, but also stellar mass and redshift. Correlations of SFE with the offset from the main-sequence and the compactness of the starburst are less clear. The increase of the molecular gas depletion timescale with M* now revealed by low M* SFGs at z>1 and observed at z=0 is in contrast to the admitted constant molecular gas depletion timescale and the linear Kennicutt-Schmidt relation. We confirm an increase of the molecular gas fraction (fgas) from z~0.2 to z~1.2, followed by a very mild increase toward higher redshifts. At each redshift fgas shows a large dispersion due to the dependence of fgas on M*, producing a gradient of increasing fgas with decreasing M*. We provide the first measure of fgas of z>1 SFGs at the low-M* end (10^{9.4} < M*/Msun < 10^{9.9}), reaching a mean fgas = 0.69+/-0.18, which shows a clear fgas upturn. Finally, we find evidence for a non-universal dust-to-gas ratio among high-redshift SFGs and sub-mm galaxies, local spirals and ULIRGs with near-solar metallicities., 21 pages, 16 figures. Accepted in A&A

We discuss strong gravitational lensing by multiple objects along any line of sight. The probability for strong gravitational lensing by more than one lens is small, but a number of strong lens systems in which more than one separate lens contribute significantly to the lensing potential will be detected in the large sample of lens systems compiled with new instruments. Using multi-lens ray-tracing, we estimate the likelihood for gravitational lensing by two lenses at different redshifts and investigate typical image geometries and magnification cross sections. We find that, for a cosmology with Omega_M=0.3 and Omega_Lambda=0.7, about one in twenty lens systems consist of two lenses with merging caustics. Multiple lens systems differ from single lenses. They have a larger multiple imaging cross section and significantly differ in the image configuration. The external shear induced by a nearby galaxy, group or cluster can affect image positions even for more widely separated lens pairs. Both of these effects must be accounted for in lens modelling. We also show how the presence of aligned discs in the pair of lensing galaxies can lead to very large high-magnification cross sections. Multiple lens systems will be important in future, both for constraining lens models of individual systems and for statistical lensing., Comment: 9 pages, 12 figures. MNRAS, submitted. Changed format of figures to jpg. A ps file of the paper including all figures can be obtained from http://www.astro.rug.nl/~ole/papers/double/paper.ps.gz

A large fraction of the luminous distant submm-wave galaxies recently detected using SCUBA on the JCMT appear to be associated with interacting optical counterparts. We investigate these systems using a simple hierarchical clustering model of galaxy evolution, in which the large luminosity of the SCUBA galaxies is assumed to be generated at the epoch of galaxy mergers in a burst of either star formation activity or the fuelling of an active galactic nucleus (AGN). The models are well constrained by the observed spectrum of the FIR/submm background radiation and the 60-micron counts of low-z IRAS galaxies. The ratio between the total amount of energy released during mergers and the mass of dark matter involved must increase sharply with z at z, 18 pages, 12 figures, in press at MNRAS. Final proof version