The SCUBA Half-Degree Extragalactic Survey -- I. Survey motivation, design and data processing

Abstract

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) (02 h 18 m − 05 • ) and the Lockman Hole East (10 h 52 m + 57 • ). 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 cospatial 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 δz < ∼ 0.5 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 arcmin 2 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 sourceextraction routines give a source density of 650 ± 50 sources deg −2 > 3σ 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.

The SCUBA Half-Degree Extragalactic Survey - II. Submillimetre maps, catalogue and number counts

“…They were observed with a resolution of 14.8 and 7.5 arcsec at 850 and 450 μm, respectively, with SCUBA (Holland et al 1999) on the 15-m JCMT atop Mauna Kea in Hawaii. A detailed account of the survey design and observing strategy is given in Mortier et al (2005) but is summarized briefly here. The observing strategy consists of making three overlapping jiggle maps for each of six different chop throws (30, 44 and 68 arcsec) and chop position angle (PA; 0 • and 90 • in RA/Dec.…”

“…For all data taken on or after 2002 December 6 the known dead bolometer 'G9' was manually removed from further analysis. Groups dealt with the presence of a 16-sample noise spike in the data in different ways, as first noted by Borys et al (2004) and Sawicki & Webb (2005) (see also Mortier et al 2005); this is further discussed in Appendix A.…”

“…Reduction steps were performed by each group independently using some combination of SURF (SCUBA User Reduction Facility; Jenness & Lightfoot 1998) and their own locally developed codes. The basic steps of the analysis procedure are described in Mortier et al (2005). Each reduction group has made different choices with respect to various detailed steps, which are described in Table 1.…”

“…While the total number of SMGs detected over the lifetime of the instrument 1 is now ∼400, these are mainly drawn from small ( 100 arcmin 2 ) fields spread all over the sky, each observed and reduced by different groups using different techniques and source identification criteria. The desire to obtain a well-characterized sample of hundreds of SMGs in a large, contiguous area was the motivation for the SCUBA Half-Degree Extragalactic Survey (SHADES; Mortier et al 2005;van Kampen et al 2005).…”

Properties of the Scuba-2 850㎛ Sources in the XMM-LSS Field

“…Result of this study can provide useful criteria for identifying the candidate protocluster around the triple SMG system. In the XMM field, studies for SMGs usually have been conducted using sub-millimeter imaging data in SCUBA Half-Degree Extragalactic Survey (SHADES; Mortier et al 2005) program which is blank-field extragalactic survey taken by the SCUBA on the JCMT. Subaru/XM M -N ewton Deep Field (SXDF) centered at (α 2000 , δ 2000 ) = (02 h 18 m 00 s , -05…”