In the local Universe, most galaxies are dominated by stars, with less than ten per cent of their visible mass in the form of gas. Determining when most of these stars formed is one of the central issues of observational cosmology. Optical and ultraviolet observations of high-redshift galaxies (particularly those in the Hubble Deep Field) have been interpreted as indicating that the peak of star formation occurred between redshifts of 1 and 1.5. But it is known that star formation takes place in dense clouds, and is often hidden at optical wavelengths because of extinction by dust in the clouds. Here we report a deep submillimetre-wavelength survey of the Hubble Deep Field; these wavelengths trace directly the emission from dust that has been warmed by massive star-formation activity. The combined radiation of the five most significant detections accounts for 30-50 per cent of the previously unresolved background emission in this area. Four of these sources appear to be galaxies in the redshift range 2 < z < 4, which, assuming these objects have properties comparable to local dust-enshrouded starburst galaxies, implies a star-formation rate during that period about a factor of five higher than that inferred from the optical and ultraviolet observations. Recent years have seen the first meaningful attempts to determine the global star-formation history of the Universe, using the combined information provided by deep redshift surveys (for example, the Canada France Redshift Survey 1 ) reaching z Ϸ 1, and the statistics of Lyman-limit galaxies 2 at higher redshifts in, for example, the Hubble Deep Field (HDF) 3-5 . The results 6 imply that the starformation and metal-production rates were about 10 times greater at z Ϸ 1 than in the local Universe, that they peaked at a redshift in the range z Ϸ 1-1:5, and that they declined to values comparable to those observed at the present day at z Ϸ 4.These conclusions, derived from optical-ultraviolet data, may however be misleading, because the absorbing effects of dust within distant galaxies undergoing massive star-formation may have distorted our picture of the evolution of the high-redshift Universe in two ways. First, the star-formation rate (SFR) in known highredshift objects is inevitably underestimated unless some correction for dust obscuration is included in deriving the rest-frame ultraviolet luminosity. Second, it is possible that an entire population of heavily dust-enshrouded high-redshift objects, as expected in some models of elliptical galaxy formation 7 , have gone undetected in the optical-ultraviolet surveys. The extent of the former remains controversial 8-11 , while the possibility of the latter has until now been impossible to investigate. Submillimetre cosmologyAt high redshifts (z Ͼ 1), the strongly-peaked far-infrared radiation emitted by star-formation regions in distant galaxies is redshifted into the submillimetre waveband, and the steep spectral index of this emission on the long-wavelength side of the peak, at l Ϸ 100 m in the rest-frame, result...

We describe updates to the redMaPPer algorithm, a photometric red-sequence cluster finder specifically designed for large photometric surveys. The updated algorithm is applied to 150 deg 2 of Science Verification (SV) data from the Dark Energy Survey (DES), and to the Sloan Digital Sky Survey (SDSS) DR8 photometric data set. The DES SV catalog is locally volume limited, and contains 786 clusters with richness λ > 20 (roughly equivalent to M 500c 10 14 h −1 70 M ) and 0.2 < z < 0.9. The DR8 catalog consists of 26311 clusters with 0.08 < z < 0.6, with a sharply increasing richness threshold as a function of redshift for z 0.35. The photometric redshift performance of both catalogs is shown to be excellent, with photometric redshift uncertainties controlled at the σ z /(1 + z) ∼ 0.01 level for z 0.7, rising to ∼ 0.02 at z ∼ 0.9 in DES SV. We make use of Chandra and XMM X-ray and South Pole Telescope Sunyaev-Zeldovich data to show that the centering performance and massrichness scatter are consistent with expectations based on prior runs of redMaPPer on SDSS data. We also show how the redMaPPer photo-z and richness estimates are relatively insensitive to imperfect star/galaxy separation and small-scale star masks.

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.

We describe the WFCAM Science Archive (WSA), which is the primary point of access for users of data from the wide-field infrared camera WFCAM on the United Kingdom Infrared Telescope (UKIRT), especially science catalogue products from the UKIRT Infrared Deep Sky Survey (UKIDSS). We describe the database design with emphasis on those aspects of the system that enable users to fully exploit the survey datasets in a variety of different ways. We give details of the database-driven curation applications that take data from the standard nightly pipeline-processed and calibrated files for the production of science-ready survey datasets. We describe the fundamentals of querying relational databases with a set of astronomy usage examples, and illustrate the results.Comment: 28 pages, 18 figures; accepted for publication in MNRAS (2007 November 8

Accepted by MNRAS. 30 pages, 15 figures (some at reduced resolution due to upload restrictions - full res version at http://surveys.roe.ac.uk/wsa/pubs.html)This paper defines the UKIRT Infrared Deep Sky Survey (UKIDSS) Early Data Release (EDR). UKIDSS is a set of five large near-infra-red surveys defined by Lawrence et al. (2006), being undertaken with the UK Infra-red Telescope (UKIRT) Wide Field Camera (WFCAM). The programme began in May 2005 and has an expected duration of seven years. Each survey uses some or all of the broadband filter complement ZYJHK. The EDR is the first public release of data to the European Southern Observatory (ESO) community. All worldwide releases occur after a delay of 18 months from the ESO release. The EDR provides a small sample dataset, ~50 sq.deg (about 1% of the whole of UKIDSS), that is a lower limit to the expected quality of future survey data releases. In addition, an EDR+ dataset contains all EDR data plus extra data of similar quality, but for areas not observed in all of the required filters (amounting to ~220 sq.deg). The first large data release, DR1, will occur in mid-2006. We provide details of the observational implementation, the data reduction, the astrometric and photometric calibration, and the quality control procedures. We summarise the data coverage and quality (seeing, ellipticity, photometricity, depth) for each survey and give a brief guide to accessing the images and catalogues from the WFCAM Science Archive

We report the discovery of XMMXCS J2215.9Ϫ1738, a massive galaxy cluster at , which was found z p 1.45 in the XMM Cluster Survey. The cluster candidate was initially identified as an extended X-ray source in archival XMM data. Optical spectroscopy shows that six galaxies within a ∼60Љ diameter region lie at . z p 1.45 ‫ע‬ 0.01 Model fits to the X-ray spectra of the extended emission yield keV (90% confidence); if there is ϩ2.7 kT p 7.4 Ϫ1.8 an undetected central X-ray point source, then keV. The bolometric X-ray luminosity is ϩ2.6 kT p 6.5 L p Ϫ1.8 X ergs s Ϫ1 over a 2 Mpc radial region. The measured , which is the highest for any known cluster ϩ0.8 44 4.4 # 10 T Ϫ0.6 X at , suggests that this cluster is relatively massive for such a high redshift. The redshift of XMMXCS z 1 1 J2215.9Ϫ1738 is the highest currently known for a spectroscopically confirmed cluster of galaxies.

This paper describes a serendipitous galaxy cluster survey that we plan to conduct with the XMM X-ray satellite. We have modeled the expected properties of such a survey for three di †erent cosmological models, using an extended Press-Schechter formalism combined with a detailed characterization of the expected capabilities of the European Photon Imaging Camera (EPIC) camera on board XMM. We estimate that, over the 10 yr design lifetime of XMM, the EPIC camera will image a total of^800 deg2 in Ðelds suitable for the serendipitous detection of clusters of galaxies. For the presently favored low-density model with a cosmological constant, our simulations predict that this survey area would yield a catalog of more than 8000 clusters, ranging from poor to very rich systems, with around 750 detections above z \ 1. A low-density open universe yields similar numbers, though with a di †erent redshift distribution, while a critical-density universe gives considerably fewer clusters. This dependence of catalog properties on cosmology means that the proposed survey will place strong constraints on the values of and The survey would also facilitate a variety of follow-up projects, including the quan-) 0 ) " . tiÐcation of evolution in the cluster X-ray luminosity-temperature relation, the study of high-redshift galaxies via gravitational lensing, follow-up observations of the Sunyaev-Zeldovich e †ect, and foreground analyses of cosmic microwave background maps.

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