A combined re-analysis of existing blank-field SCUBA surveys: comparative 850-mu m source lists, combined number counts, and evidence for strong clustering of the bright submillimetre galaxy population on arcminute scales

Since the advent of Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT), a series of complementary surveys has resolved the bulk of the far-infrared extragalactic background into discrete sources. This has revealed a population of heavily dust-obscured sources at high redshift (z > 1) undergoing an intense period of massive star-forming activity with inferred star formation rates of several hundred to several thousand solar masses per year. Taken together, these existing surveys cover a total area of 460 arcmin(2) to a range of depths, but combining the results has hitherto been complicated by the fact that different survey groups have used different methods of data reduction and source extraction. In this paper, we re-reduce and re-analyse all of the blank-field surveys to date in an almost identical manner to that employed in the 'SCUBA 8-mJy Survey'. Comparative source catalogues are given which include a number of new significant source detections as well as failing to confirm some of those objects previously published. These new source catalogues have been combined to produce the most accurate number counts to date from 2 to 12.5 mJy. We find N(> 4 mJy) = 620(-190)(+110) deg(-2), N(> 6 mJy) = 310(-100)(+60) deg(-2), N(> 8 mJy) = 150(-60)(+40) deg(-2) and N(> 10 mJy) = 40(-20)(+20) deg(-2) after correcting for the effects of incompleteness, flux-density boosting and contamination from spurious/confused detections. Furthermore, the cumulative number counts appear to steepen beyond S-850 > 8 mJy, which could indicate an intrinsic turnover in the underlying luminosity function placing an upper limit on the luminosity (and hence mass) of a high-redshift galaxy. We have also investigated the clustering properties of the bright S-850 > 5 mJy SCUBA population by means of two-point angular correlation functions. We find a similar or equal to 3.5 sigma excess of pairs within the first 100 arcsec over that expected from a Poisson distribution. Fits of a standard power law of the form omega(theta) = A theta(-delta) to the angular correlation functions for S-850 > 5 mJy are limited in accuracy by the small number of source detections but appear to be broadly consistent with those measured for extremely red objects. Nearest-neighbour analyses further support strong clustering on arcmin scales, rejecting the null hypothesis that the distribution of the submillimetre sources is random at the 95 per cent confidence level for S-850 > 5 mJy, and at the 99 per cent confidence level for S-850 > 7 mJy.