A submillimetre survey of Lyman α haloes in the SA 22 protocluster at z=3.1

We present the results from a submillimetre (submm) survey of a sample of 23 giant Lyman a (Ly alpha) emitting nebulae in the overdensity at z = 3.09 in the SA 22 field. These objects, which have become known as Lya Blobs (LABs), have a diverse range of morphology and surface brightness, but the nature of their power source remains unclear, with both cooling flows or starburst/active galactic nucleus (AGN) ionized winds being possibilities. Using the Submillimetre Common-User Bolometer Array ( SCUBA) submm camera on the James Clerk Maxwell Telescope (JCMT), we measure the 850-mu m flux of a sample of LABs. We present detections of submm emission from four LABs at > 3.5 sigma individually, and obtain a modest statistical detection of the full sample at an average flux of 3.0 +/- 0.9 mJy. These detections indicate significant activity within the LAB haloes, with bolometric luminosities in the ultra-luminous regime (> 10(12) L-circle dot), equivalent to a star formation rate (SFR) of similar to 10(3) M-circle dot yr(-1). By comparisons to LAB-like objects in other regions, we show that there is an apparent trend (although weak) between observed Lya emission and bolometric luminosity. Combined with our detection of ultraluminous activity in this population and the lack of any strong morphological correlations in our sample, this provides evidence that the interaction of an ambient halo of gas with a Galactic-scale 'superwind' is most likely to be responsible for the extended Lya emission in the majority of LABs. Assuming the extent of the LABs reflects outflows from a superwind, we estimate the age of starbursts in the submm LABs to be in the range 10-100 Myr. Using the average submm flux of the LABs, we determine an SFR density in the SA 22 structure of > 3M(circle dot) yr(-1) Mpc(-3), greater than the field at this epoch. The submm detection of these four LABs means there are now seven luminous submm galaxies in the z = 3.09 structure in SA 22, making this the largest known association of these intensely active galaxies. This clustering further strengthens the proposed evolutionary link between these galaxies and local cluster ellipticals. Finally, we suggest that the highly extended Lya haloes (which define the LAB class) may be a common feature of the submm galaxy population in general, underlining their role as potentially important sources of metal enrichment and heating of the intergalactic medium (IGM).