The SCUBA Bright Quasar Survey (SBQS): 850-mu m observations of the z greater than or similar to 4 sample

We present initial results of a new, systematic search for massive star formation in the host galaxies of the most luminous and probably most massive z 4 radio-quiet quasars (M-B less than or equal to -27.5; nuL(nu)(1450 Angstrom) > 10(13) L.). The survey, undertaken at 850 mum using SCUBA at the James Clerk Maxwell Telescope (JCMT), has a target sensitivity limit of 3 sigma similar to 10 mJy, set to identify sources suitable for detailed follow-up, e.g. continuum mapping and molecular line diagnostics. A total of 38 z greater than or similar to 4 radio-quiet quasars have been observed at 850 mum, of which eight were detected (>3sigma) with S-850mum greater than or similar to 10 mJy (submillimetre-loud). The new detections almost triple the number of optically selected, submillimetre-loud z greater than or similar to 4 radio-quiet quasars known to date. We include a detailed description of how our quasar sample is defined in terms of radio and optical properties. As a by-product of our selection procedure, we have identified 17 radio-loud quasars with z greater than or similar to 4. There is no strong evidence for trends in either detectability or 850-mum flux with absolute magnitude, M-B. We find that the weighted mean flux of the undetected sources is 2.0 +/- 0.6 mJy, consistent with an earlier estimate of similar to3 mJy based on more sensitive observations of a sample z greater than or similar to 4 radio-quiet quasars. This corresponds to an inferred star formation rate of similar to1000 M. yr(-1), similar to Arp220. The typical star formation time-scale for the submillimetre-bright sources is similar to1 Gyr, 10 times longer than the typical accretion-driven e-folding time-scale of similar to5 x 10(7) yr. Our 850-mum detection of the z = 4.4 quasar PSS J1048+4407, when analysed in conjunction with 1.2-mm single-dish and interferometric observations, suggests that this source is resolved on angular scales of 1-2 aresec (6-12 kpc). In addition, we present a new optical spectrum of this source, identifying it as a broad absorption line (BAL) quasar. The new redshift is outside that covered in a recent CO line search, highlighting the need for accurate redshifts for the observation and interpretation of high-redshift line studies.