The SCUBA Bright Quasar Survey (SBQS): 850‐μm observations of the z ≳ 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 radio‐quiet quasars . The survey, undertaken at 850 μm using SCUBA at the James Clerk Maxwell Telescope (JCMT), has a target sensitivity limit of , set to identify sources suitable for detailed follow‐up, e.g. continuum mapping and molecular line diagnostics. A total of 38 radio‐quiet quasars have been observed at 850 μm, of which eight were detected (>3 σ ) with (submillimetre‐loud). The new detections almost triple the number of optically selected, submillimetre‐loud 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 . There is no strong evidence for trends in either detectability or 850‐μm flux with absolute magnitude, M B . We find that the weighted mean flux of the undetected sources is , consistent with an earlier estimate of ∼3 mJy based on more sensitive observations of a sample radio‐quiet quasars. This corresponds to an inferred star formation rate of ∼1000 M ⊙  yr −1 , similar to Arp220. The typical star formation time‐scale for the submillimetre‐bright sources is ∼1 Gyr, 10 times longer than the typical accretion‐driven e‐folding time‐scale of ∼. Our 850‐μm detection of the 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 . 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.