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A submillimetre census of star-formation at high-redshift Coppin, Kristen Erin Kathryn

Abstract

Maps, source catalogue and number counts are presented for the largest, most complete and uniform extragalactic submillimetre survey ever undertaken: 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). These SCUBA maps cover 720 arcmin² with an RMS noise level of about 2 mJy and have uncovered > 100 submillimetre galaxies. Individual source lists from four groups drawn within the SHADES team (of which this thesis provides a detailed account of one of the reductions) are compared in terms of source flux densities and positions and combined to produce a 120-object SHADES catalogue. This catalogue is 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, deboosted flux densities are presented for each submillimetre galaxy using a recipe developed here. 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. Differential and integral source number counts are given and the differential counts are found to be 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. Based on the SHADES results, an 850 μm survey complete down to 2 mJy would resolve 20-30 per cent of the Far-IR background into point sources. In order to help constrain spectral energy distributions (SEDs) and hence redshifts for the SHADES galaxies, a follow-up effort was undertaken using the Submillimetre High Angular Resolution Camera (SHARC-II; Dowell 2003) at the Caltech Submillimetre Observatory (CSO). The maps and 350 μm flux estimates of a subset of the SHADES catalogue are presented. Using available redshift estimates, I attempt to characterise the SEDs in terms of the dust temperature and far-IR luminosity. Star-formation rates and dust mass estimates for the sample are derived and the SMG population is confirmed to be dominated by very massive ([Asymptotically = to] 5 x 10 ¹⁰ M₀), luminous ([Asymptotically = to] 10 ¹² L₀) star-forming (SFR [Asymptotically = to] 1000 M₀ yr⁻¹) galaxies with intrinsic dust temperatures of [Asymptotically = to] 35 K.

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