Robert G. Sharp

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 I¼m 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 I¼m, of which eight were detected (>3Iƒ) 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-I¼m flux with absolute magnitude, MB. 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 MâS™ 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-I¼m 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.

A sensitive submillimetre survey of broad absorption-line quasars

Using the SCUBA bolometer array on the JCMT, we have carried out a submillimetre (submm) survey of Broad Absorption Line quasars (BALQs). The sample has been chosen to match, in redshift and optical luminosity, an existing benchmark 850� m sample of radio-quiet quasars, allowing a direct comparison of the submm properties of BAL quasars relative to the parent radio-quiet population. We reach a submm limit 1σ �1.5mJy at 850� m, allowing a more rigorous measure of the submm properties of BAL quasars than previous studies. Our submm photometry complements extensive observations at other wavelengths, in particular X-rays with Chandra and infrared with Spitzer. To compare the 850� m flux distribution of BALQs with that of the non-BAL quasar benchmark sample, we employ a suite of statistical methods, including survival analysis and a novel Bayesian derivation of the underlying flux distribution. Although there are no strong grounds for rejecting the null hypothesis that BALQs on the whole have the same submm properties as non-BAL quasars, we do find tentative evidence (1–4 percent significance from a K–S test and survival analysis) for a dependence of submm flux on the equivalent width of the characteristic C IV broad absorption line. If this effect is real— submm activity is linked to the absorption strength of the outflow— it has implications either for the evolution of AGN and their connection with star formation in their host galaxies, or for unification models of AGN.

The Circumnuclear Starburst in M83

We present results from near‐infrared integral‐field spectroscopy of the circumnuclear starburst in M83, using the CIRPASS instrument on Gemini South. The combination of Paβ, CO (6,3), and [Fe II] equivalent width measurements over large contiguous regions allows us to track the spatial propagation of star formation across the ringlet, which is too heavily obscured to be properly analysed at optical wavelengths. We find the clearest evidence yet for an age gradient, with the youngest clusters found closest to where the dust lane crosses the ringlet. We discuss the implications for gas fueling by the bar.