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The PRobe far-Infrared Mission for Astrophysics (PRIMA) concept aims to perform mapping with spectral coverage and sensitivities inaccessible to previous FIR space telescopes. PRIMA's imaging instrument, PRIMAger, provides unique hyperspectral imaging simultaneously covering 25–235 µm. We synthesize images representing a deep, 1500 h deg−2 PRIMAger survey, with realistic instrumental and confusion noise. We demonstrate that we can construct catalogues of galaxies with a high purity (>95 per cent) at a source density of 42 k deg−2 using PRIMAger data alone. Using the XID+ deblending tool, we show that we measure fluxes with an accuracy better than 20 per cent to flux levels of 0.16, 0.80, 9.7, and 15 mJy at 47.4, 79.7, 172, and 235 µm, respectively. These are a factor of ∼2 and ∼3 fainter than the classical confusion limits for 72–96 and 126–235 µm, respectively. At |$1.5 \le z \le 2$|⁠ , we detect and accurately measure fluxes in 8–10 of the 10 channels covering 47–235 µm for sources with |$2 \lesssim \log ({\rm SFR}) \lesssim 2.5$|⁠ , a 0.5 dex improvement on what might be expected from the classical confusion limit. Recognizing that PRIMager will operate in a context where high-quality data will be available at other wavelengths, we investigate the benefits of introducing additional prior information. We show that by introducing even weak prior flux information when employing a higher source density catalogue (more than one source per beam), we can obtain accurate fluxes an order of magnitude below the classical confusion limit for 96–235 µm. [ABSTRACT FROM AUTHOR]

We present 101- and 151-GHz ALMA continuum images for 85 fields selected from Herschel observations that have 500-μm flux densities >80 mJy and 250–500-μm colours consistent with z > 2, most of which are expected to be gravitationally lensed or hyperluminous infrared galaxies. Approximately half of the Herschel 500-μm sources were resolved into multiple ALMA sources, but 11 of the 15 brightest 500-μm Herschel sources correspond to individual ALMA sources. For the 37 fields containing either a single source with a spectroscopic redshift or two sources with the same spectroscopic redshift, we examined the colour temperatures and dust emissivity indices. The colour temperatures only vary weakly with redshift and are statistically consistent with no redshift-dependent temperature variations, which generally corresponds to results from other samples selected in far-infrared, submillimetre, or millimetre bands but not to results from samples selected in optical or near-infrared bands. The dust emissivity indices, with very few exceptions, are largely consistent with a value of 2. We also compared spectroscopic redshifts to photometric redshifts based on spectral energy distribution templates designed for infrared-bright high-redshift galaxies. While the templates systematically underestimate the redshifts by ∼15 per cent, the inclusion of ALMA data decreases the scatter in the predicted redshifts by a factor of ∼2, illustrating the potential usefulness of these millimetre data for estimating photometric redshifts. [ABSTRACT FROM AUTHOR]

We analyse the molecular and atomic emission lines of 71 bright Herschel -selected galaxies between redshifts 1.4 and 4.6 detected by the Atacama Large Millimeter/submillimeter Array. These lines include a total of 156 CO, [C i] , and H2O emission lines. For 46 galaxies, we detect two transitions of CO lines, and for these galaxies we find gas properties similar to those of other dusty star-forming galaxy (DSFG) samples. A comparison to photodissociation models suggests that most of Herschel -selected galaxies have similar interstellar medium conditions as local infrared-luminous galaxies and high-redshift DSFGs, although with denser gas and more intense far-ultraviolet radiation fields than normal star-forming galaxies. The line luminosities agree with the luminosity scaling relations across five orders of magnitude, although the star formation and gas surface density distributions (i.e. Schmidt–Kennicutt relation) suggest a different star formation phase in our galaxies (and other DSFGs) compared to local and low-redshift gas-rich, normal star-forming systems. The gas-to-dust ratios of these galaxies are similar to Milky Way values, with no apparent redshift evolution. Four of 46 sources appear to have CO line ratios in excess of the expected maximum (thermalized) profile, suggesting a rare phase in the evolution of DSFGs. Finally, we create a deep stacked spectrum over a wide rest-frame frequency (220–890 GHz) that reveals faint transitions from HCN and CH, in line with previous stacking experiments. [ABSTRACT FROM AUTHOR]

We present spectroscopic measurements for 71 galaxies associated with 62 of the brightest high-redshift submillimetre sources from the Southern fields of the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS), while targeting 85 sources which resolved into 142. We have obtained robust redshift measurements for all sources using the 12-m Array and an efficient tuning of ALMA to optimize its use as a redshift hunter, with 73 per cent of the sources having a robust redshift identification. Nine of these redshift identifications also rely on observations from the Atacama Compact Array. The spectroscopic redshifts span a range 1.41 < z < 4.53 with a mean value of 2.75, and the CO emission line full-width at half-maxima range between |$\rm 110\, km\, s^{-1} \lt FWHM \lt 1290\, km\, s^{-1}$| with a mean value of ∼500 km s−1, in line with other high- z samples. The derived CO(1-0) luminosity is significantly elevated relative to line-width to CO(1-0) luminosity scaling relation, which is suggestive of lensing magnification across our sources. In fact, the distribution of magnification factors inferred from the CO equivalent widths is consistent with expectations from galaxy–galaxy lensing models, though there is a hint of an excess at large magnifications that may be attributable to the additional lensing optical depth from galaxy groups or clusters. [ABSTRACT FROM AUTHOR]

Using the Eight MIxer Receiver (EMIR) instrument on the Institut de RadioAstronomie Millimétrique (IRAM) 30-m telescope, we conducted a spectroscopic redshift search of seven z phot ∼ 4 submillimetre bright galaxies selected from the Herschel Bright Sources sample with fluxes at 500 μm greater than 80 mJy. For four sources, we obtained spectroscopic redshifts between 3.4 < z < 4.1 through the detection of multiple CO-spectral lines with J  ≥ 3. Later, we detected low- J transitions for two of these sources with the Green Bank Telescope including the CO(1–0) transition. For the remaining three sources, more data are needed to determine the spectroscopic redshift unambiguously. The measured CO luminosities and line widths suggest that all these sources are gravitationally lensed. These observations demonstrate that the 2 mm window is indispensable to confirm robust spectroscopic redshifts for z < 4 sources. Finally, we present an efficient graphical method to correctly identify spectroscopic redshifts. [ABSTRACT FROM AUTHOR]

Quadruply lensed quasars are extremely rare objects, but incredibly powerful cosmological tools. Only few dozen are known in the whole sky. Here we present the spectroscopic confirmation of two new quadruplets WG0214-2105 and WG2100-4452 discovered by Agnello & Spiniello (2018) within the Dark Energy Survey public footprints. We have conducted spectroscopic follow-up of these systems with the Southern African Large Telescope as part of a program that aims at confirming the largest possible number of strong gravitational lenses in the equatorial and Southern hemisphere. For both systems, we present the sources spectra that allowed us to estimate their redshifts and unambiguously confirm their lensing nature. For the brighter deflector (WG2100-4452) we measure the spectroscopic redshift and the stellar velocity dispersion from optical absorption lines in the spectrum. For the other system we infer the lens redshift from photometry, being the quality of the spectra not good enough. We obtain photometry for both lenses, directly from multiband images, isolating the lenses from the quasars. One of the quadruplets, WG0214-2105, was also observed by Pan-STARRS, allowing us to estimate the apparent brightness of each quasar image at two different epochs, and thus to find evidence for flux variability. This result could suggest a microlensing event for the faintest components, although intrinsic variability cannot be excluded with only two epochs. Finally, we present simple lens models for both quadruplets, obtaining Einstein radii, singular isothermal ellipsoid velocity dispersions, ellipticities, and position angles of the lenses, as well as time-delay predictions assuming a concordance cosmological model. [ABSTRACT FROM AUTHOR]

We have modelled ~0.1 arcsec resolution Atacama Large Millimetre/submillimeter Array imaging of six strong gravitationally lensed galaxies detected by the Herschel Space Observatory. Our modelling recovers mass properties of the lensing galaxies and, by determining magnification factors, intrinsic properties of the lensed submillimetre sources. We find that the lensed galaxies all have high ratios of star formation rate to dust mass, consistent with or higher than the mean ratio for high-redshift submillimetre galaxies and low-redshift ultraluminous infrared galaxies. Source reconstruction reveals that most galaxies exhibit disturbed morphologies. Both the cleaned image plane data and the directly observed interferometric visibilities have been modelled, enabling comparison of both approaches. In the majority of cases, the recovered lens models are consistent between methods, all six having mass density profiles that are close to isothermal. However, one system with poor signal to noise shows mildly significant differences. [ABSTRACT FROM AUTHOR]

We present the first detailed analysis of three extragalactic fields (IRAC Dark Field, ELAIS-N1, ADF-S) observed by the infrared satellite, AKARI, using an optimized data analysis toolkit specifically for the processing of extragalactic point sources. The InfaRed Camera (IRC) on AKARI complements the SpitzerSpace Telescope via its comprehensive coverage between 8–24 μm filling the gap between the Spitzer/IRAC and MIPS instruments. Source counts in the AKARI bands at 3.2, 4.1, 7, 11, 15 and 18 μm are presented. At near-infrared wavelengths, our source counts are consistent with counts made in other AKARI fields and in general with Spitzer/IRAC (except at 3.2 μm where our counts lie above). In the mid-infrared (11 – 18 μm), we find our counts are consistent with both previous surveys by AKARI and the Spitzer peak-up imaging survey with the InfraRed Spectrograph (IRS). Using our counts to constrain contemporary evolutionary models, we find that although the models and counts are in agreement at mid-infrared wavelengths there are inconsistencies at wavelengths shortward of 7 μm, suggesting either a problem with stellar subtraction or indicating the need for refinement of the stellar population models. We have also investigated the AKARI/IRC filters, and find an active galactic nucleus selection criteria out to z < 2 on the basis of AKARI 4.1, 11, 15 and 18 μm colours. [ABSTRACT FROM AUTHOR]

We model the z ≥ 6.6 Ly α luminosity function to estimate the number of lensed high-z Ly α emitters that may be detected by the Euclid Deep Survey. To span the whole range of possible predictions, we exploit two Ly a luminosity function models and two strong gravitational lensing models from the literature.We show that the planned Euclid Deep Survey observing 40 deg2 over the 920-1850 nm wavelength range down to a flux limit of Flim = 5 × 10-17 erg s-1 cm-2 will enable us to find between~0.85 and~1.82 deg-2 lensed Ly α emitters at z ≥ 6.6 depending on the adopted Ly α luminosity function and strong gravitational lensing model. The obvious [O II], [O III] and Hβ contaminants of the Ly α lensed population will be identified with the help of Euclid's spectral resolving power, while the Square Kilometre Array (SKA) will enable the identification of the interloper population of H α emitters. By combining Euclid and the SKA, we will thus be able to identify, for the first time, a sample of ~34 to ~73 lensed Ly α emitters at z ≥ 6.6. [ABSTRACT FROM AUTHOR]

We present a study of the molecular gas properties in a sample of 98 HI - flux selected spiral galaxies within~25 Mpc, using the CO J=3-2 line observed with the James Clerk Maxwell Telescope. We use the technique of survival analysis to incorporate galaxies with CO upper limits into our results. Comparing the group and Virgo samples, we find a larger mean H2 mass in the Virgo galaxies, despite their lower mean HI mass. This leads to a significantly higher H2 to HI ratio for Virgo galaxies. Combining our data with complementary Ha star formation rate measurements, Virgo galaxies have longer molecular gas depletion times compared to group galaxies, due to their higher H2 masses and lower star formation rates. We suggest that the longer depletion times may be a result of heating processes in the cluster environment or differences in the turbulent pressure. From the full sample, we find that the molecular gas depletion time has a positive correlation with the stellar mass, indicative of differences in the star formation process between low- and high-mass galaxies, and a negative correlation between the molecular gas depletion time and the specific star formation rate. [ABSTRACT FROM AUTHOR]

We present the first galaxy counts at 18 μm using the Japanese AKARI satellite's survey at the North Ecliptic Pole (NEP), produced from the images from the NEP-Deep and NEP-Wide surveys covering 0.6 and 5.8 deg2, respectively. We describe a procedure using a point source filtering algorithm to remove background structure and a minimum variance method for our source extraction and photometry that delivers the optimum signal to noise for our extracted sources, confirming this by comparison with standard photometry methods. The final source counts are complete and reliable over three orders of magnitude in flux density, resulting in sensitivities (80 per cent completeness) of 0.15 and 0.3 mJy for the NEP-Deep and NEP-Wide surveys, respectively, a factor of 1.3 deeper than previous catalogues constructed from this field. The differential source counts exhibit a characteristic upturn from Euclidean expectations at around a milliJansky and a corresponding evolutionary bump between 0.2–0.4 mJy consistent with previous mid-infrared surveys with ISO and Spitzer at 15 and 24 μm. We compare our results with galaxy evolution models confirming the striking divergence from the non-evolving scenario. The models and observations are in broad agreement implying that the source counts are consistent with a strongly evolving population of luminous infrared galaxies at redshifts higher than unity. Integrating our source counts down to the limit of the NEP survey at the 150 μJy level we calculate that AKARI has resolved approximately 55 per cent of the 18 μm cosmic infrared background relative to the predictions of contemporary source count models. [ABSTRACT FROM PUBLISHER]

The first deep blank-field 450 μm map (1σ ≈ 1.3 mJy) from the Submillimetre Common-User Bolometer Array-2 SCUBA-2 Cosmology Legacy Survey (S2CLS), conducted with the James Clerk Maxwell Telescope (JCMT) is presented. Our map covers 140 arcmin2 of the Cosmological Evolution Survey field, in the footprint of the Hubble Space Telescope (HST) Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey. Using 60 submillimetre galaxies detected at ≥3.75σ, we evaluate the number counts of 450-μm-selected galaxies with flux densities S450 > 5 mJy. The 8 arcsec JCMT beam and high sensitivity of SCUBA-2 now make it possible to directly resolve a larger fraction of the cosmic infrared background (CIB, peaking at λ ∼ 200 μm) into the individual galaxies responsible for its emission than has previously been possible at this wavelength. At S450 > 5 mJy, we resolve (7.4 ± 0.7) × 10−2 MJy sr−1 of the CIB at 450 μm (equivalent to 16 ± 7 per cent of the absolute brightness measured by the Cosmic Background Explorer at this wavelength) into point sources. A further ∼40 per cent of the CIB can be recovered through a statistical stack of 24 μm emitters in this field, indicating that the majority (≈60 per cent) of the CIB at 450 μm is emitted by galaxies with S450 > 2 mJy. The average redshift of 450 μm emitters identified with an optical/near-infrared counterpart is estimated to be 〈z〉 = 1.3, implying that the galaxies in the sample are in the ultraluminous class ($L_{\rm IR}\approx 1.1\times 10^{12}\,{\rm \text{L}_{\odot }}$). If the galaxies contributing to the statistical stack lie at similar redshifts, then the majority of the CIB at 450 μm is emitted by galaxies in the luminous infrared galaxy (LIRG) class with LIR > 3.6 × 1011 L⊙. [ABSTRACT FROM AUTHOR]

This is the first paper in a series that presents a multiwavelength analysis of the archetype ultraluminous infrared galaxy IRAS F10214+4724, a gravitationally lensed, starburst/active galactic nucleus at z = 2.3. Here we present a new lens model and spatially resolved radio data, as well as a deep Hubble Space Telescope (HST) F160W map. The lens modelling employs a Bayesian Markov chain Monte Carlo algorithm with extended source, forward ray tracing. Using these high-resolution HST, Multi-Element Radio Linked Interferometer Network (MERLIN) and Very Large Array (VLA) maps, the algorithm allows us to constrain the level of distortion to the continuum spectral energy distribution resulting from emission components with differing magnification factors, due to their size and proximity to the caustic. Our lens model finds that the narrow-line region, and by proxy the active nucleus, is preferentially magnified. This supports previous claims that preferential magnification could mask the expected polycyclic aromatic hydrocarbon spectral features in the Spitzer mid-infrared spectrum which roughly trace the star-forming regions. Furthermore, we show that the arc-to-counter-image flux ratio is not a good estimate of the magnification in this system, despite its common use in the IRAS F10214+4724 literature. Our lens modelling suggests magnifications of μ ∼ 15–20 ± 2 for the HST F814W, MERLIN 1.7 GHz and VLA 8 GHz maps, significantly lower than the canonical values of μ = 50–100 often used for this system. Systematic errors such as the dark matter density slope and colocation of stellar and dark matter centroids dominate the uncertainties in the lens model at the 40 per cent level. [ABSTRACT FROM AUTHOR]

The Planck Early Release Compact Source Catalogue (ERCSC) has offered the first opportunity to accurately determine the luminosity function of dusty galaxies in the very local Universe (i.e. distances ≲100 Mpc), at several (sub-)millimetre wavelengths, using blindly selected samples of low-redshift sources, unaffected by cosmological evolution. This project, however, requires careful consideration of a variety of issues including the choice of the appropriate flux density measurement, the separation of dusty galaxies from radio sources and from Galactic sources, the correction for the CO emission, the effect of density inhomogeneities and more. We present estimates of the local luminosity functions at 857 GHz (350 μm), 545 GHz (550 μm) and 353 GHz (850 μm) extending across the characteristic luminosity L⋆, and a preliminary estimate over a limited luminosity range at 217 GHz (1382 μm). At 850 μm and for luminosities L ≳ L⋆ our results agree with previous estimates, derived from the Submillimeter Common-User Bolometer Array (SCUBA) Local Universe Galaxy Survey, but are higher than the latter at L ≲ L⋆. We also find good agreement with estimates at 350 and 500 μm based on preliminary Herschel survey data. [ABSTRACT FROM AUTHOR]

ABSTRACT The James Clerk Maxwell Telescope Nearby Galaxies Legacy Survey (NGLS) comprises an H i-selected sample of 155 galaxies spanning all morphological types with distances less than 25 Mpc. We describe the scientific goals of the survey, the sample selection and the observing strategy. We also present an atlas and analysis of the CO J=3 - 2 maps for the 47 galaxies in the NGLS which are also part of the Spitzer Infrared Nearby Galaxies Survey. We find a wide range of molecular gas mass fractions in the galaxies in this sample and explore the correlation of the far-infrared luminosity, which traces star formation, with the CO luminosity, which traces the molecular gas mass. By comparing the NGLS data with merging galaxies at low and high redshift, which have also been observed in the CO J=3 - 2 line, we show that the correlation of far-infrared and CO luminosity shows a significant trend with luminosity. This trend is consistent with a molecular gas depletion time which is more than an order of magnitude faster in the merger galaxies than in nearby normal galaxies. We also find a strong correlation of the LFIR/ LCO(3-2) ratio with the atomic-to-molecular gas mass ratio. This correlation suggests that some of the far-infrared emission originates from dust associated with atomic gas and that its contribution is particularly important in galaxies where most of the gas is in the atomic phase. [ABSTRACT FROM AUTHOR]

ABSTRACT We have made the first map of CO( J= 3-2) emission covering the disc of the edge-on galaxy, NGC 4631, which is known for its spectacular gaseous halo. The strongest emission, which we model with a Gaussian ring, occurs within a radius of 5 kpc. Weaker disc emission is detected out to radii of 12 kpc, the most extensive molecular component yet seen in this galaxy. From comparisons with infrared data, we find that CO( J= 3-2) emission more closely follows the hot dust component, rather than the cold dust, consistent with it being a good tracer of star formation. The first maps of R3−2/1−0, H2 mass surface density and star formation efficiency (SFE) have been made for the inner 2.4 kpc radius region. Only 20 per cent of the star formation occurs in this region and excitation conditions are typical of galaxy discs, rather than of central starbursts. The SFE suggests long gas consumption time-scales ( >109 yr). The velocity field is dominated by a steeply rising rotation curve in the region of the central molecular ring followed by a flatter curve in the disc. A very steep gradient in the rotation curve is observed at the nucleus, providing the first evidence for a central concentration of mass: Mdyn= 5 × 107 M⊙ within a radius of 282 pc. The velocity field shows anomalous features indicating the presence of molecular outflows; one of them is associated with a previously observed CO( J= 1-0) expanding shell. Consistent with these outflows is the presence of a thick ( z up to 1.4 kpc) CO( J= 3-2) disc. We suggest that the interaction between NGC 4631 and its companion(s) has agitated the disc and also initiated star formation which was likely higher in the past than it is now. These may be necessary conditions for seeing prominent haloes. [ABSTRACT FROM AUTHOR]

ABSTRACT An analysis of large-area CO J= 3-2 maps from the James Clerk Maxwell Telescope for 12 nearby spiral galaxies reveals low velocity dispersions in the molecular component of the interstellar medium. The three lowest luminosity galaxies show a relatively flat velocity dispersion as a function of radius while the remaining nine galaxies show a central peak with a radial fall-off within 0.2-0.4 r25. Correcting for the average contribution due to the internal velocity dispersions of a population of giant molecular clouds, the average cloud-cloud velocity dispersion across the galactic discs is 6.1 ± 1.0 km s −1 (standard deviation of 2.9 km s −1), in reasonable agreement with previous measurements for the Galaxy and M33. The cloud-cloud velocity dispersion derived from the CO data is on average two times smaller than the H i velocity dispersion measured in the same galaxies. The low cloud-cloud velocity dispersion implies that the molecular gas is the critical component determining the stability of the galactic disc against gravitational collapse, especially in those regions of the disc which are H 2 dominated. The cloud-cloud velocity dispersion shows a significant positive correlation with both the far-infrared luminosity, which traces the star formation activity, and the K-band absolute magnitude, which traces the total stellar mass. For three galaxies in the Virgo cluster, smoothing the data to a resolution of 4.5 kpc (to match the typical resolution of high-redshift CO observations) increases the measured velocity dispersion by roughly a factor of 2, comparable to the dispersion measured recently in a normal galaxy at z= 1. This comparison suggests that the mass and star formation rate surface densities may be similar in galaxies from z= 0 to 1 and that the high star formation rates seen at z= 1 may be partly due to the presence of physically larger molecular gas discs. [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 used Spitzer Space Telescope 3.6, 8.0, 70 and 160 μm data, James Clerk Maxwell Telescope HARP-B CO J= (3–2) data, National Radio Astronomy Observatory 12 m telescope CO J= (1–0) data and Very Large Array H i data to investigate the relations among polycyclic aromatic hydrocarbons (PAHs), cold (∼20 K) dust, molecular gas and atomic gas within NGC 2403, an SABcd galaxy at a distance of 3.13 Mpc. The dust surface density is mainly a function of the total (atomic and molecular) gas surface density and galactocentric radius. The gas-to-dust ratio monotonically increases with radius, varying from ∼100 in the nucleus to ∼400 at 5.5 kpc. The slope of the gas-to-dust ratio is close to that of the oxygen abundance, suggesting that metallicity strongly affects the gas-to-dust ratio within this galaxy. The exponential scale length of the radial profile for the CO J= (3–2) emission is statistically identical to the scale length for the stellar continuum-subtracted 8 μm (PAH 8 μm) emission. However, CO J= (3–2) and PAH 8 μm surface brightnesses appear uncorrelated when examining sub-kpc-sized regions. [ABSTRACT FROM AUTHOR]

We present results on low-resolution mid-infrared (MIR) spectra of 70 IR-luminous galaxies obtained with the infrared spectrograph (IRS) onboard Spitzer. We selected sources from the European Large Area Infrared Survey with mJy and photometric or spectroscopic . About half of the samples are quasi-stellar objects (QSOs) in the optical, while the remaining sources are galaxies, comprising both obscured active galactic nuclei (AGN) and starbursts. Redshifts were obtained from optical spectroscopy, photometric redshifts and the IRS spectra. The later turn out to be reliable for obscured and/or star-forming sources, thus becoming an ideal complement to optical spectroscopy for redshift estimation. We estimate monochromatic luminosities at several rest-frame wavelengths, equivalent widths and luminosities for the polycyclic aromatic hydrocarbon (PAH) features, and strength of the silicate feature in individual spectra. We also estimate integrated 8–1000 μm IR luminosities via spectral energy distribution fitting to MIR and far-IR (FIR) photometry from the Spitzer Wide-Area Infrared Extragalactic survey and the MIR spectrum. Based on these measurements, we classify the spectra using well-known IR diagnostics, as well as a new one that we propose, into three types of source: those dominated by an unobscured AGN, mostly corresponding to optical quasars (QSOs), those dominated by an obscured AGN and starburst-dominated sources. Starbursts concentrate at favoured by the shift of the 7.7-μm PAH band into the selection 15-μm band, while AGN spread over the range. Star formation rates (SFR) are estimated for individual sources from the luminosity of the PAH features. An estimate of the average PAH luminosity in QSOs and obscured AGN is obtained from the composite spectrum of all sources with reliable redshifts. The estimated mean SFR in the QSOs is , but the implied FIR luminosity is 3–10 times lower than that obtained from stacking analysis of the FIR photometry, suggesting destruction of the PAH carriers by energetic photons from the AGN. The SFR estimated in obscured AGN is two to three times higher than in QSOs of similar MIR luminosity. This discrepancy might not be due to luminosity effects or selection bias alone, but could instead indicate a connection between obscuration and star formation. However, the observed correlation between silicate absorption and the slope of the NIR to MIR spectrum is compatible with the obscuration of the AGN emission in these sources being produced in a dust torus. [ABSTRACT FROM AUTHOR]

We investigate the photometric redshift accuracy achievable with the AKARI infrared data in deep multiband surveys, such as in the North Ecliptic Pole field. We demonstrate that the passage of redshifted polycyclic aromatic hydrocarbons (PAH) and silicate features into the mid-infrared wavelength window covered by AKARI is a valuable means to recover the redshifts of starburst galaxies. To this end, we have collected a sample of ∼60 galaxies drawn from the Great Observatories Origins Deep Survey-North Field with spectroscopic redshift and photometry from 3.6 to 24 μm, provided by the Spitzer, Infrared Space Observatory and AKARI satellites. The infrared spectra are fitted using synthetic galaxy spectral energy distributions which account for starburst and active nuclei emission. For ∼90 per cent of the sources in our sample, the redshift is recovered with an accuracy per cent. A similar analysis performed on a set of simulated spectra shows that the AKARI infrared data alone can provide photometric redshifts accurate to per cent (1σ) at . At higher redshifts, the PAH features are shifted outside the wavelength range covered by AKARI and the photo- z estimates rely on the less prominent stellar bump; the accuracy achievable in this case on is ∼10–15 per cent, provided that the active galactic nuclei contribution to the infrared emission is subdominant. Our technique is no more prone to redshift aliasing than optical-ultraviolet photo- z, and it may be possible to reduce this aliasing further with the addition of submillimetre and/or radio data. [ABSTRACT FROM AUTHOR]

We present the optical-to-submillimetre spectral energy distributions (SEDs) for 33 radio and mid-infrared (mid-IR) identified submillimetre galaxies discovered via the SHADES 850-μm SCUBA imaging in the Subaru- XMM Deep Field (SXDF). Optical data for the sources come from the SXDF and mid- and far-IR fluxes from SWIRE. We obtain photometric redshift estimates for our sources using optical and IRAC 3.6- and 4.5-μm fluxes. We then fit SED templates to the longer wavelength data to determine the nature of the far-IR emission that dominates the bolometric luminosity of these sources. The IR template fits are also used to resolve ambiguous identifications and cases of redshift aliasing. The redshift distribution obtained broadly matches previous results for submillimetre sources and on the SHADES SXDF field. Our template fitting finds that active galactic nuclei, while present in about 10 per cent of our sources, do not contribute significantly to their bolometric luminosity. Dust heating by starbursts, with either Arp220 or M82 type SEDs, appears to be responsible for the luminosity in most sources (23/33 are fitted by Arp220 templates, 2/33 by the warmer M82 templates). 8/33 sources, in contrast, are fitted by a cooler cirrus dust template, suggesting that cold dust has a role in some of these highly luminous objects. Three of our sources appear to have multiple identifications or components at the same redshift, but we find no statistical evidence that close associations are common among our SHADES sources. Examination of rest-frame K-band luminosity suggests that ‘downsizing’ is underway in the submillimetre galaxy population, with lower redshift systems lying in lower mass host galaxies. Of our 33 identifications six are found to be of lower reliability but their exclusion would not significantly alter our conclusions. [ABSTRACT FROM AUTHOR]

We present a comparison between the SCUBA (Submillimetre Common User Bolometer Array) Half Degree Extragalactic Survey (SHADES) at 450 and in the Lockman Hole East with a deep Spitzer Space Telescope survey at conducted in guaranteed time. Using stacking analyses we demonstrate a striking correspondence between the galaxies contributing the submm extragalactic background light, with those likely to dominate the backgrounds at Spitzer wavelengths. Using a combination BRIzK plus Spitzer photometric redshifts, we show that at least a third of the Spitzer-identified submm galaxies at appear to reside in overdensities when the density field is smoothed at 0.5–2 Mpc comoving diameters, supporting the high-redshift reversal of the local star formation–galaxy density relation. We derive the dust-shrouded cosmic star formation history of galaxies as a function of assembled stellar masses. For model stellar masses , this peaks at lower redshifts than the ostensible maximum for submm point sources, adding to the growing consensus for ‘downsizing’ in star formation. Our surveys are also consistent with ‘downsizing’ in mass assembly. Both the mean star formation rates and specific star formation rates are in striking disagreement with some semi-analytic predictions from the Millenium Simulation. The discrepancy could either be resolved with a top-heavy initial mass function, or a significant component of the submm flux heated by the interstellar radiation field. [ABSTRACT FROM AUTHOR]

We derive the properties of dusty tori in active galactic nuclei from the comparison of observed spectral energy distributions (SEDs) of SDSS quasars and a precomputed grid of torus models. The observed SEDs comprise SDSS photometry, Two-Micron All-Sky Survey J, H and K data, whenever available, and mid-infrared (mid-IR) data from the Spitzer Wide-area InfraRed Extragalactic Survey. The adopted model is that of Fritz, Franceschini & Hatziminaoglou. The fit is performed by standard -minimization; the model, however, can be a multicomponent comprising a stellar and a starburst component, whenever necessary. Models with low equatorial optical depth, τ9.7, were allowed as well as ‘traditional’ models with , corresponding to and the results were compared. Fits using high optical depth tori models only produced dust more compactly distributed than in the configuration where all τ9.7 models were permitted. Tori with decreasing dust density with the distance from the centre were favoured while there was no clear preference for models with or without angular variation of the dust density. The computed outer radii of the tori are of some tens of parsecs large but can reach, in a few cases, a few hundreds of parsecs. The mass of dust, MDust, and IR luminosity, LIR, integrated in the wavelength range between 1 and 1000 μm, do not show significant variations with redshift, once the observational biases are taken into account. Objects with 70-μm detections, representing 25 per cent of the sample, are studied separately and the starburst contribution (whenever present) to the IR luminosity can reach, in the most extreme but very few cases, 80 per cent. [ABSTRACT FROM AUTHOR]

We present estimates of the photometric redshifts, stellar masses and star formation histories of sources in the Submillimetre Common-User Bolometer Array (SCUBA) HAlf Degree Extragalactic Survey (SHADES). This paper describes the 60 SCUBA sources detected in the Lockman Hole covering an area of ∼320 arcmin2. Using photometry spanning the B band to 8 μm, we find that the average SCUBA source forms a significant fraction of its stars in an early period of star formation and that most of the remainder forms in a shorter more intense burst around the redshift it is observed. This trend does not vary significantly with source redshift. However, the sources show a clear increase in stellar mass with redshift, consistent with downsizing. In terms of spectral energy distribution types, only two out of the 51 sources we have obtained photometric redshifts for are best fitted by a quasar-like spectrum, with approximately 80 per cent of the sources being best fitted with late-type spectra (Sc, Im and starburst). By including photometry at 850 μm, we conclude that the average SCUBA source is forming stars at a rate somewhere between 6 and 30 times the rate implied from the rest-frame optical in a dust obscured burst and that this burst creates 15–65 per cent of the total stellar mass. Using a simplistic calculation, we estimate from the average star formation history that between one in five and one in 15 bright galaxies in the field over the interval will at some point in their lifetime experience a similar energetic dusty burst of star formation. Finally, we compute the evolution of the star formation rate density and find it peaks around . [ABSTRACT FROM AUTHOR]

We have studied the submillimetre (submm) properties of the following classes of near-infrared-selected (NIR-selected) massive galaxies at high redshifts: BzK-selected star-forming galaxies ( BzKs); distant red galaxies (DRGs); and extremely red objects (EROs). We used the SCUBA HAlf Degree Extragalactic Survey (SHADES), the largest uniform submm survey to date. Partial overlap of SIRIUS/NIR images and SHADES in Subaru/ XMM–Newton deep field has allowed us to identify four submm-bright NIR-selected galaxies, which are detected in the mid-IR, 24μ m, and the radio, 1.4GHz. We find that all of our submm-bright NIR-selected galaxies satisfy the BzK selection criteria, i.e. , except for one galaxy whose B− z and z− K colours are however close to the BzK colour boundary. Two of the submm-bright NIR-selected galaxies satisfy all of the selection criteria we considered, i.e. they belong to the BzK–DRG–ERO overlapping population, or ‘extremely red’ BzKs. Although these extremely red BzKs are rare (0.25 arcmin−2), up to 20 per cent of this population could be submm galaxies. This fraction is significantly higher than that found for other galaxy populations studied here. Via a stacking analysis, we have detected the 850-μ m flux of submm-faint BzKs and EROs in our SCUBA maps. While the contribution of z∼ 2 BzKs to the submm background is about 10–15 per cent and similar to that from EROs typically at z∼ 1, BzKs have a higher fraction (∼30 per cent) of submm flux in resolved sources compared with EROs and submm sources as a whole. From the spectral energy distribution (SED) fitting analysis for both submm-bright and submm-faint BzKs, we found no clear signature that submm-bright BzKs are experiencing a specifically luminous evolutionary phase, compared with submm-faint BzKs. An alternative explanation might be that submm-bright BzKs are more massive than submm-faint ones. [ABSTRACT FROM AUTHOR]

We present maps, source catalogue and number counts of the largest, most complete and unbiased extragalactic submillimetre survey: the 850-μm SCUBA Half-Degree Extragalactic Survey (SHADES). Using the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT), SHADES mapped two separate regions of sky: the Subaru/ XMM–Newton Deep Field (SXDF) and the Lockman Hole East (LH). Encompassing 93 per cent of the overall acquired data (i.e. data taken up to 2004 February 1), these SCUBA maps cover 720 arcmin2 with a rms noise level of about 2 mJy and have uncovered >100 submillimetre galaxies. In order to ensure the utmost robustness of the resulting source catalogue, data reduction was independently carried out by four subgroups within the SHADES team, providing an unprecedented degree of reliability with respect to other SCUBA catalogues available from the literature. Individual source lists from the four groups were combined to produce a robust 120-object SHADES catalogue; an invaluable resource for follow-up campaigns aiming to study the properties of a complete and consistent sample of submillimetre galaxies. For the first time, we present deboosted flux densities for each submillimetre galaxy found in a large survey. Extensive simulations and tests were performed separately by each group in order to confirm the robustness of the source candidates and to evaluate the effects of false detections, completeness and flux density boosting. Corrections for these effects were then applied to the data to derive the submillimetre galaxy source counts. SHADES has a high enough number of detected sources that meaningful differential counts can be estimated, unlike most submillimetre surveys which have to consider integral counts. We present differential and integral source number counts and find that the differential counts are better fit with a broken power law or a Schechter function than with a single power law; the SHADES data alone significantly show that a break is required at several mJy, although the precise position of the break is not well constrained. We also find that a 850-μm survey complete down to 2 mJy would resolve 20–30 per cent of the far-infrared background into point sources. [ABSTRACT FROM AUTHOR]

Since the advent of Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT), a series of complementary surveys has resolved the bulk of the far-infrared extragalactic background into discrete sources. This has revealed a population of heavily dust-obscured sources at high redshift undergoing an intense period of massive star-forming activity with inferred star formation rates of several hundred to several thousand solar masses per year. Taken together, these existing surveys cover a total area of 460 arcmin2 to a range of depths, but combining the results has hitherto been complicated by the fact that different survey groups have used different methods of data reduction and source extraction. In this paper, we re-reduce and re-analyse all of the blank-field surveys to date in an almost identical manner to that employed in the ‘SCUBA 8-mJy Survey’. Comparative source catalogues are given which include a number of new significant source detections as well as failing to confirm some of those objects previously published. These new source catalogues have been combined to produce the most accurate number counts to date from 2 to 12.5 mJy. We find and after correcting for the effects of incompleteness, flux-density boosting and contamination from spurious/confused detections. Furthermore, the cumulative number counts appear to steepen beyond , which could indicate an intrinsic turnover in the underlying luminosity function placing an upper limit on the luminosity (and hence mass) of a high-redshift galaxy. We have also investigated the clustering properties of the bright SCUBA population by means of two-point angular correlation functions. We find a ≃3.5σ excess of pairs within the first 100 arcsec over that expected from a Poisson distribution. Fits of a standard power law of the form to the angular correlation functions for are limited in accuracy by the small number of source detections but appear to be broadly consistent with those measured for extremely red objects. Nearest-neighbour analyses further support strong clustering on arcmin scales, rejecting the null hypothesis that the distribution of the submillimetre sources is random at the 95 per cent confidence level for , and at the 99 per cent confidence level for . [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]

The Submillimetre Common-User Bolometer Array (SCUBA) Half-Degree Extragalactic Survey (SHADES) is a major new blank-field extragalactic submillimetre (submm) survey currently underway at the James Clerk Maxwell Telescope (JCMT). Ultimately, SHADES aims to cover half a square degree at 450 and 850 μm to a 4σ depth of ≃ 8 mJy at 850 μm. Two fields are being observed, the Subaru/ XMM–Newton Deep Field (SXDF) and the Lockman Hole East . The survey has three main aims: (i) to investigate the population of high-redshift submm galaxies and the cosmic history of massive dust-enshrouded star formation activity; (ii) to investigate the clustering properties of submm-selected galaxies in order to determine whether these objects could be progenitors of present-day massive ellipticals; and (iii) to investigate the fraction of submm-selected sources that harbour active galactic nuclei. To achieve these aims requires that the submm data be combined with co-spatial information spanning the radio-to-X-ray frequency range. Accordingly, SHADES has been designed to benefit from ultra-deep radio imaging obtained with the Very Large Array (VLA), deep mid-infrared observations from the Spitzer Space Telescope, submm mapping by the Balloon-borne Large Aperture Submillimetre Telescope ( BLAST), deep near-infrared imaging with the United Kingdom Infrared Telescope, deep optical imaging with the Subaru Telescope and deep X-ray observations with the XMM–Newton observatory. It is expected that the resulting extensive multiwavelength data set will provide complete photometric redshift information accurate to as well as detailed spectral energy distributions for the vast majority of the submm-selected sources. In this paper, the first of a series on SHADES, we present an overview of the motivation for the survey, describe the SHADES survey strategy, provide a detailed description of the primary data-analysis pipeline and demonstrate the superiority of our adopted matched-filter source-extraction technique over, for example, Emerson-II style methods. We also report on the progress of the survey. As of 2004 February, 720 arcmin2 had been mapped with SCUBA (about 40 per cent of the anticipated final total area) to a median 1σ depth of 2.2 mJy per beam at 850 μm (25 mJy per beam at 450 μm), and the source-extraction routines give a source density of sources at 850 μm. Although uncorrected for Eddington bias, this source density is more than sufficient for providing enough sources to answer the science goals of SHADES, once half a square degree is observed. A refined reanalysis of the original 8-mJy survey Lockman hole data was carried out in order to evaluate the new data-reduction pipeline. Of the 17 most secure sources in the original sample, 12 have been reconfirmed, including 10 of the 11 for which radio identifications were previously secured. [ABSTRACT FROM AUTHOR]

We report on a search for the optical counterparts of selected sources from the Far-Infrared Background (FIRBACK) survey in the European Large Area ISO Survey (ELAIS) N2 field. Applying a likelihood ratio technique to optical catalogues from the Isaac Newton Telescope – Wide Field Survey (INT-WFS), we found optical identifications for 33 out of 55 FIRBACK sources in this field. These were then reassessed in the light of associations with the ELAIS final catalogue for the N2 field, to yield a final set of 31 associations. We have investigated the nature of this population through a comparison of their observed spectral energy distributions (SEDs) with predictions from radiative transfer models which simulate the emission from both cirrus and starburst components. We find the far-infrared sources to be 80 per cent starburst galaxies with their starburst component at a high optical depth. The resulting SEDs were used to estimate far-infrared luminosities, star formation rates (SFRs), dust temperatures and dust masses. The N2 FIRBACK population is found to consist of four suspected ultraluminous infrared galaxies (ULIRGs) with and , a number of luminous infrared galaxies (LIRGs) with moderate star formation rates and and a population of low-redshift quiescently star-forming galaxies. We also discuss the implications of these results for current evolutionary models. [ABSTRACT FROM AUTHOR]

We present the multiwavelength properties and catalogue of the 15 μm and 1.4 GHz radio sources detected in the European Large AreaISOSurvey (ELAIS) areas N1 and N2. Using the optical data from the Wide Field Survey we use a likelihood ratio method to search for the counterparts of the 1056 and 691 sources detected at 15 μm and 1.4 GHz, respectively, down to flux limits ofand. We find that∼92 per cent of the 15 μmELAISsources have an optical counterpart down to. All mid-infrared (IR) sources with fluxeshave an optical counterpart. The magnitude distribution of the sources shows a well-defined peak at relatively bright magnitudes. The mid-IR-to-optical and radio-to-optical flux diagrams are presented and discussed in terms of actual galaxy models. About 15 per cent of the sources are bright galactic stars; of the extragalactic objects∼65 per cent are compatible with being normal or starburst galaxies and∼25 per cent active galactic nuclei (AGNs). Objects with mid-IR-to-optical fluxes larger than 100 are found, comprising∼20 per cent of the sample. We suggest that that these sources are highly obscured luminous and ultraluminous starburst galaxies and AGNs. [ABSTRACT FROM AUTHOR]

We present the final analysis of the European Large AreaInfrared Space Observatory(ISO) Survey (ELAIS) 15-μm observations, carried out with the ISO Camera (ISOCAM) instrument on board theISO.The data-reduction method, known as the Lari Method, is based on a mathematical model of the behaviour of the detector and was specifically designed for the detection of faint sources in ISOCAM/ISO Photopolarimeter (ISOPHOT) data. The method is fully interactive and leads to very reliable and complete source lists.The resulting catalogue includes 1923 sources detected with signal-to-noise ratio ofin the 0.5–100 mJy flux range and over an area of 10.85 deg2 split into four fields, making it the largest non-serendipitous extragalactic source catalogue obtained to date from theISOdata.This paper presents the concepts underlying the data-reduction method together with its latest enhancements. The data-reduction process, the production and basic properties of the resulting catalogue are discussed. The catalogue quality is assessed by means of detailed simulations, optical identifications and comparison with previous analyses. [ABSTRACT FROM AUTHOR]

We present a cross-correlation of the European Large AreaInfrared Space Observatory(ISO) survey (ELAIS) with the ELAIS Deep X-ray Survey of the N1 and N2 fields. There are sevenChandrapoint sources with matches in the ELAIS Final Analysis 15-μm catalogue, out of a total of 28 extragalacticISOsources present in theChandrafields. Five of these are consistent with active galactic nuclei (AGN) giving an AGN fraction of∼19 per cent in the 15-μm flux range 0.8–6 mJy. We have co-added the hard X-ray fluxes of the individually undetectedISOsources and find a low significance detection consistent with star formation in the remaining population. We combine our point source cross-correlation fraction with theXMM–Newtonobservations of the Lockman Hole andChandraobservations of theHubble Deep FieldNorth to constrain source count models of the mid-infrared galaxy population. The low dust-enshrouded AGN fraction in ELAIS implied by the number of cross-identifications between the ELAIS mid-infrared sample and theChandrapoint sources is encouraging for the use of mid-infrared surveys to constrain the cosmic star formation history, provided there are not further large undetected populations of Compton-thick AGN. [ABSTRACT FROM AUTHOR]

This paper discusses the properties of the European Large AreaISOSurvey (ELAIS) 15-μm quasars and tries to establish a robust method of quasar selection for future use within theSpitzerWide-Area Infrared Extragalactic Survey (SWIRE) framework. The importance of good-quality ground-based optical data is stressed, both for the selection of candidates and for the estimation of photometric redshifts. Colour–colour plots and template fitting are used for these purposes. The properties of the 15-μm quasar sample, including variability and black hole masses, are studied and compared to the properties of other quasars that lie within the same fields but have no mid-infrared counterparts. The two subsamples do not present substantial differences and are believed to come from the same parent population. [ABSTRACT FROM AUTHOR]

We present a re-analysis of the European Large AreaInfrared Space Observatory(ISO) Survey (ELAIS) 90-μm observations carried out with ISOPHOT, an instrument on board theISOof the European Space Agency. With more than 12 deg2, the ELAIS survey is the largest area covered byISOin a single programme and is about one order of magnitude deeper than theIRAS100-μm survey. The data analysis is presented and was mainly performed with thephotinteractive analysis software but using the pairwise method of Stickel et al. for signal processing from edited raw data to signal per chopper plateau. The ELAIS 90-μm catalogue contains 237 reliable sources with fluxes larger than 70 mJy and is available in the electronic version of this article. Number counts are presented and show an excess above the no-evolution model prediction. This confirms the strong evolution detected at shorter (15μm) and longer (170μm) wavelengths in otherISOsurveys. The ELAIS counts are in agreement with previous works at 90μm and in particular with the deeper counts extracted from the Lockman hole observations. Comparison with recent evolutionary models show that the models of Franceschini et al. and Guiderdoni et al. (which includes a heavily extinguished population of galaxies) give the best fit to the data. Deeper observations are nevertheless required to discriminate better between the model predictions in the far-infrared, and are scheduled with theSpitzer Space Telescope, which has already started operating, and will also be performed byASTRO-F. [ABSTRACT FROM AUTHOR]

In this paper, we present the results of calculations of cross-sections and rate coefficients for rotationally inelastic transitions in methanol (CH3OH), in its ground torsional state, induced by collisions with para-H2 in its ground rotational state. The interaction potential was calculated by means of many-body perturbation theory, and the corresponding cross-sections computed using the coupled states approximation to the Schrödinger equation for the CH3OH–H2 system. The rate coefficients have been calculated for kinetic temperatures in the range . We found that, although the rate coefficients for para-H2 are qualitatively similar to those computed for He, the collisional propensity rules are less pronounced when the perturber is para-H2 than when it is He. The rate coefficients for CH3OH–H2 tend to be larger than for CH3OH–He, a tendency which is anticipated from a comparison of the corresponding interaction potentials. Although our discussion is in terms of E-type methanol, the analogous results for A-type methanol and para-H2 are also available. Our calculations are the first to consider H2 as a collision partner for CH3OH and are directly relevant to the interpretation of observations of methanol in the interstellar medium. [ABSTRACT FROM AUTHOR]

We present the final band-merged European Large-Area ISO Survey (ELAIS) Catalogue at 6.7, 15, 90 and 175 μm, and the associated data at U, g′, r′, i′, Z, J, H, K and 20 cm. The origin of the survey, infrared and radio observations, data-reduction and optical identifications are briefly reviewed, and a summary of the area covered and the completeness limit for each infrared band is given. A detailed discussion of the band-merging and optical association strategy is given. The total Catalogue consists of 3762 sources. 23 per cent of the 15-μm sources and 75 per cent of the 6.7-μm sources are stars. For extragalactic sources observed in three or more infrared bands, colour–colour diagrams are presented and discussed in terms of the contributing infrared populations. Spectral energy distributions (SEDs) are shown for selected sources and compared with cirrus, M82 and Arp220 starburst, and active galactic nuclei (AGN) dust torus models. Spectroscopic redshifts are tabulated, where available. For the N1 and N2 areas, the Isaac Newton Telescope ugriz Wide Field Survey permits photometric redshifts to be estimated for galaxies and quasars. These agree well with the spectroscopic redshifts, within the uncertainty of the photometric method [∼10 per cent in for galaxies]. The redshift distribution is given for selected ELAIS bands and colour–redshift diagrams are discussed. There is a high proportion of ultraluminous infrared galaxies (log10 of 1–1000 μm luminosity ) in the ELAIS Catalogue (14 per cent of 15-μm galaxies with known z), many with Arp220-like SEDs. 10 per cent of the 15-μm sources are genuine optically blank fields to : these must have very high infrared-to-optical ratios and probably have , so are high-luminosity dusty starbursts or Type 2 AGN. Nine hyperluminous infrared galaxies and nine extremely red objects (EROs) are found in the survey. The latter are interpreted as ultraluminous dusty infrared galaxies at . The large numbers of ultraluminous galaxies imply very strong evolution in the star formation rate between z= 0 and 1. There is also a surprisingly large population of luminous , cool (cirrus-type SEDs) galaxies, with , implying . [ABSTRACT FROM AUTHOR]

Despite extensive observational efforts, a convincing optical/infrared identification of the brightest submm source in the Hubble Deep Field, HDF 850.1, has remained elusive after almost four years. This failure is all the more notable given the availability of supporting multifrequency data of unparalleled depth, and subarcsec positional accuracy for the submm/mm source. Consequently, HDF 850.1 has become a test case for the possibility that the most violently star-forming objects in the Universe are too red and/or distant to be seen in the deepest optical images. Here we report the discovery of the galaxy counterpart of HDF 850.1. This object has been revealed by careful analysis of a new, deep K′ image of the HDF obtained with the Subaru 8.2-m telescope. Its reality is confirmed by a similar analysis of the HST NICMOS F160W image of the same region. This object is extremely faint ( K≃ 23.5), clumpy (on subarcsec scales) and very red ( I− K > 5.2; H− K= 1.4 ± 0.35). The likelihood that it is the correct galaxy counterpart is strongly reinforced by a reanalysis of the combined MERLIN+VLA 1.4-GHz map of the field, which provides a new radio detection of HDF 850.1 only 0.1 arcsec from the new near-infrared counterpart, and with sufficient positional accuracy to exclude all previously considered alternative optical candidates. We have calculated new confidence limits on the estimated redshift of HDF 850.1 in the light of the new radio detection, and find . We have also determined the scalelength, and hence estimated the mass of the apparently nearby (0.5 arcsec distant) elliptical galaxy 3−586.0. From this we calculate that the flux density of HDF 850.1 has been boosted by a factor of ≃3 through gravitational lensing by this intervening elliptical, consistent with predictions that a small but significant fraction of blank-field submm sources are lensed by foreground galaxies. We discuss the wider implications of these results for the submm population and cosmic star formation history. [ABSTRACT FROM AUTHOR]

We present deep wide-field -band observations of six Hyperluminous Infrared Galaxies (HLIRGs) spanning a redshift range . The sample resides in a wide variety of environments, from the field to Abell 2 clusters, with a mean galaxy–HLIRG clustering amplitude of . The range in environments, and the mean clustering level, are both greater than those seen in local IR-luminous galaxies, from which we infer that the range of galaxy evolution processes driving IR-luminous galaxy evolution at is greater than locally, and includes mergers between gas-rich spiral galaxies in the field, but also includes encounters in clusters and hierarchical build-up. The similarity in the range of environments and mean clustering amplitude between our sample and QSOs over a similar redshift range is consistent with the interpretation where evolutionary connections between IR-luminous galaxies and QSOs are stronger at than locally, and that, at these redshifts, the processes that drive QSO evolution are similar to those that drive IR-luminous galaxy evolution. From comparison of the HLIRG and QSO host galaxies we further postulate that a larger fraction of IR-luminous galaxies pass through an optical QSO stage at than locally. [ABSTRACT FROM AUTHOR]

Presents an analysis of the submillimeter common user bolometer array observation of the Hubble Deep Field. Review of the observing strategy and data acquisition; Discussion of data reduction algorithms; Consideration of source astrometry and flux calibration uncertainties.

ABSTRACT We present an analysis of two deep (75 ks) Chandra observations of the European Large Area Infrared Space Observatory (ISO) Survey (ELAIS) fields N1 and N2 as the first results from the ELAIS deep X-ray survey. This survey is being conducted in well-studied regions with extensive multiwavelength coverage. Here we present the Chandra source catalogues along with an analysis of source counts, hardness ratios and optical classifications. A total of 233 X-ray point sources are detected in addition to two soft extended sources, which are found to be associated with galaxy clusters. An overdensity of sources is found in N1 with 30 per cent more sources than N2, which we attribute to large-scale structure. A similar variance is seen between other deep Chandra surveys. The source count statistics reveal an increasing fraction of hard sources at fainter fluxes. The number of galaxy-like counterparts also increases dramatically towards fainter fluxes, consistent with the emergence of a large population of obscured sources. [ABSTRACT FROM AUTHOR]

Abstract The sources discovered in deep hard X-ray surveys with 2–8 keV fluxes of S[sub 2-8]∼ 10[sup -14] erg cm[sup -2] s[sup -1] make up the bulk of the X-ray background at these energies. Here we present detailed multiwavelength observations of three such sources from the European Large-Area ISO Survey Deep X-ray Survey. The observations include sensitive near-infrared spectroscopy with the Subaru Telescope and X-ray spectral information from the Chandra X-ray Observatory. The sources observed all have optical-to-near-infrared (near-IR) colours redder than an unobscured quasar and comprise a reddened quasar, a radio galaxy and an optically obscured active galactic nucleus (AGN). The reddened quasar is at a redshift z= 2.61 and shows a very large X-ray absorbing column of N[sub H]≈ 3 × 10[sup 23] cm[sup -2] . This contrasts with the relatively small amount of dust reddening, implying a gas-to-dust ratio along the line of sight 100 times greater than that of the Milky Way. The radio galaxy at z= 1.57 shows only narrow emission lines, but has a surprisingly soft X-ray spectrum. The softness of this spectrum indicates either an unusually low gas-to-dust ratio for the absorbing medium or X-ray emission related to the young radio source. The host galaxy is extremely red (R-K= 6.4) and its optical/near-IR spectrum is best fit by a strongly reddened (A[sub V]≈ 2) starburst. The third X-ray source discussed is also extremely red (R-K= 6.1) and lies in a close grouping of three other R-K > 6 galaxies. No emission or absorption lines were detected from this object, but its redshift (and that of one of the nearby galaxies) is constrained by spectral energy distribution fitting to be just greater than z= 1 . The extremely red colours of these two galaxies can be accounted for by old stellar populations. These observations illustrate the diverse properties of hard X-ray-selected AGN at high redshift in terms of obscuration at optical and X-ray wavelengths and the evolutionary states of their host galaxies. [ABSTRACT FROM AUTHOR]

We explore the relationship between the hard X-ray and submillimetre populations using deep Chandra observations of a large, contiguous SCUBA survey. In agreement with other recent findings, we confirm that the direct overlap is small. Of the 17 submillimetre sources detected in this field at 850 µm, only one is coincident with a Chandra source. The resulting limits imply that the majority of SCUBA sources are not powered by acive galactic nuclei (AGN), unless the central engine is obscured by Compton-thick material with a low (<1 per cent) scattered component. Furthermore, since Chandra detects only ∼5 per cent of SCUBA sources, the typical obscuration would need to be almost isotropic. The X-ray upper limits are so strong that in most cases we can also rule out a starburst spectral energy distribution at low redshift, suggesting that the majority of SCUBA sources lie at z > 1, even if they are purely starburst galaxies. Despite the low detection rate, we find evidence for strong angular clustering between the X-ray and submillimetre populations. The implication is that AGN and SCUBA sources trace the same large-scale structure but do not generally coincide. If bright submillimetre sources represent massive elliptical galaxies in formation, we suggest that (for a given galaxy) the major episode of star formation must be distinct from the period of observable quasar activity. [ABSTRACT FROM AUTHOR]

We present J- and K-band near-infrared (near-IR) photometry of a sample of mid-infrared (mid-IR) sources detected by the Infrared Space Observatory (ISO) as part of the European Large Area ISO Survey (ELAIS) and study their classification and star-forming properties. We have used the Preliminary ELAIS Catalogue for the 6.7-μm (LW2) and 15-μm (LW3) fluxes. All of the high-reliability LW2 sources and 80 per cent of the LW3 sources are identified in the near-IR survey reaching K ≈ 17.5 mag. The near-IR/mid-IR flux ratios can effectively be used to separate stars from galaxies in mid-IR surveys. The stars detected in our survey region are used to derive a new accurate calibration for the ELAIS ISOCAM data in both the LW2 and LW3 filters. We show that near- to mid-IR colour-colour diagrams can be used to classify galaxies further, as well as to study star formation. The ELAIS ISOCAM survey is found mostly to detect strongly star-forming late-type galaxies, possibly starburst-powered galaxies, and it also picks out obscured active galactic nuclei. The ELAIS galaxies yield an average mid-IR flux ratio LW2/LW3 = 0.67 ± 0.27. We discuss the f[sub v](6.7 μm)/f[sub v](15 μm) ratio as a star formation tracer using ISO and IRAS data of a local comparison sample. We find that the f[sub v](2.2 μm)/f[sub v](15 μm) ratio is also a good indicator of activity level in galaxies and conclude that the drop in the f[sub v](6.7 μm)/f[sub v](15 μm) ratio seen in strongly star-forming galaxies is a result of both an increase of 15-μm emission and an apparent depletion of 6.7-μm emission. Near-IR together with the mid-IR data make it possible to estimate the relative amount of interstellar matter in the galaxies. [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]

Abstract We present submillimetre (sub-mm) photometry for 11 hyperluminous infrared galaxies (HLIRGs, ) and use radiative transfer models for starbursts and active galactic nuclei (AGN) to examine the nature of the IR emission. In all the sources both a starburst and AGN are required to explain the total IR emission. The mean starburst fraction is 35 per cent, with a range spanning 80 per cent starburst-dominated to 80 per cent AGN-dominated. In all cases the starburst dominates at rest-frame wavelengths longwards of 50 μm, with star formation rates >500 M[sub ⊙] yr[sup -1] . The trend of increasing AGN fraction with increasing IR luminosity observed in IRAS galaxies is observed to peak in the HLIRG population, and not increase beyond the fraction seen in the brightest ultraluminous infrared galaxies (ULIRGs). The AGN and starburst luminosities correlate, suggesting that a common physical factor, plausibly the dust masses, govern the luminosities of starbursts and AGN in HLIRGs. Our results suggest that the HLIRG population is composed both of ULIRG-like galaxy mergers and of young galaxies going through their maximal star formation periods whilst harbouring an AGN. The detection of coeval AGN and starburst activity in our sources implies that starburst and AGN activity, and the peak starburst and AGN luminosities, can be coeval in active galaxies generally. When extrapolated to high z our sources have comparable observed frame sub-mm fluxes to sub-mm survey sources. At least some high-z sub-mm survey sources are therefore likely to be composed of similar galaxy populations to those found in the HLIRG population. It is also plausible from these results that high-z sub-mm sources harbour heavily obscured AGN. The differences in X-ray and sub-mm properties between HLIRGs at z∼ 1 and sub-mm sources at ∼3 implies some level of evolution between the two epochs. Either the mean AGN obscuration level is greater at z∼ 3 than at z∼ 1 , or the fraction of IR-luminous sources at z∼ 3 that contain AGN is smaller than that at z∼ 1 . [ABSTRACT FROM AUTHOR]

Abstract We present the 15-μm extragalactic source counts from the Final Analysis Catalogue of the European Large Area ISO Survey (ELAIS) Southern hemisphere field S1, extracted using the Lari method. The large number of extragalactic sources (∼350) detected over this area between about 0.5 and 100 mJy guarantee a high statistical significance of the source counts in the previously poorly covered flux density range between IRAS and the Deep ISOCAM Surveys. The bright counts in S1 (S[sub 15 μm]&gsim; 2 mJy) are significantly lower than other published ISOCAM counts in the same flux range and are consistent with a flat, Euclidean slope, suggesting the dominance of a non-evolving population. In contrast, at fainter fluxes (S[sub 15 μm]&lsim; 2 mJy) our counts show a strong departure from no-evolution models, with a very steep super-Euclidean slope down to our flux limit (∼0.5 mJy). Strong luminosity and density evolutions of the order of, respectively, L∝ (1 +z)[sup 3.0] and ρ∝ (1 +z)[sup 3.5] are needed at least for the population of star-forming galaxies in order to fit the counts and the redshift distributions observed at different fluxes. A luminosity break around 10[sup 10.8]L[sub ⊙] must be introduced in the local luminosity function of starburst galaxies in order to reproduce our sharp increase of the counts below 2 mJy and the redshift distributions observed for 15-μm sources at different flux levels. The contribution of the strongly evolving starburst population (down to 50 μJy) to the 15-μm cosmic background is estimated to be ∼2.2 nW m[sup -2] sr[sup -1], which corresponds to ∼67 per cent of the total mid-infrared background estimate. [ABSTRACT FROM AUTHOR]

We present the 15-µm luminosity function of type 1 active galactic nuclei (AGN1; quasi-stellar object + Seyfert 1). Our sample of 21 high-redshift sources is selected from the Preliminary Analysis catalogue in the S1 field of the European Large Area ISO Survey (ELAIS). To study the cosmological evolution of the AGN1 luminosity function, our sample has been combined with a local sample of 41 sources observed by IRAS. We find that the luminosity function of AGN1 at 15 µm is fairly well represented by a double-power-law-function. There is evidence for significant cosmological evolution consistent with a pure luminosity evolution (PLE) model L(z) ∝ (1 + z)[sup k[sub L]], with k[sub L] = 3.0-3.3. The value of k[sub L] depends on the existence or non-existence of an evolution cut-off at redshift ∼2, and on the adopted cosmology. From the luminosity function and its evolution we estimate a contribution of AGN1 to the cosmic infrared background (CIRB) of νI[sub ν] ∼ 6 x 10[sup -11] W m[sup -2] sr[sup -1] at 15 µm. This corresponds to ∼-2-3 per cent of the total observed CIRB at this wavelength. Under the usual assumptions of unified models for AGN, the expected contribution of the whole AGN population to the CIRB at 15 µm is 10-15 per cent. [ABSTRACT FROM AUTHOR]

We present maps, source lists and derived number counts from the largest, unbiased, extragalactic submillimetre (submm) survey so far undertaken with the SCUBA camera on the James Clerk Maxwell Telescope (JCMT). Our maps are located in two regions of sky (ELAIS N2 and Lockman-Hole E) and cover 260 arcmin[sup 2], to a typical rms noise level of σ[sub 850]≃2.5 mJy beam[sup -1] . We have reduced the data using both the standard JCMTsurf procedures, and our own IDL -based pipeline which produces zero-footprint maps and noise images. The uncorrelated noise maps produced by the latter approach have enabled us to apply a maximum likelihood method to measure the statistical significance of each peak in our maps, leading to properly quantified errors on the flux density of all potential sources. We detect 19 sources with signal-to-noise ratios (S/N)>4 , and 38 with S/N>3.5 . To assess both the completeness of this survey and the impact of source confusion as a function of flux density, we have applied our source-extraction algorithm to a series of simulated images. The result is a new estimate of the submm source counts over the flux-density range S[sub 850]≃5–15 mJy , which we compare with estimates derived by other workers, and with the predictions of a number of models. Our best estimate of the cumulative source count at S[sub 850]>8 mJy is 320 - 100 + 80 per square degree. Assuming that the majority of sources lie at z>1.5 , this result implies that the comoving number density of high-redshift galaxies forming stars at a rate in excess of 1000 M[sub ⊙] yr[sup -1] is ≃10[sup -5] Mpc[sup -3], with only a weak dependence on the precise redshift distribution. This number density corresponds to the number density of massive ellipticals with L>3–4L* in the present-day Universe , and is also the same as the comoving number density of comparably massive, passively evolving objects in the redshift band 1