A submm survey of Lyman-alpha haloes in the SA22 protocluster at z=3.1

Abstract

We present the results from a submm survey of a sample of 23 giant Lya emitting nebulae in the overdensity at z=3.09 in the SA22 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 is unclear - with cooling flows and/or AGN/starburst ionised winds being possibilities. Using the SCUBA submm camera we measure the 850um flux of a sample of LABs, detecting four LABs at >3.5sigma individually, and a modest statistical detection of the full sample at about 3mJy. These fluxes correspond to bolometric luminosities in the ultraluminous regime, with star-formation rates of about 1e3 Msun/yr. We show there is a trend between Lya luminosity and bolometric output, which suggests that a galactic scale superwind generated from starbursts of age 10-100Myr may be responsible for the Lya emission. We estimate the star-formation rate density in SA22 to be >3 Msun/yr/Mpc^3 - greater than the field at this epoch, and note that there are now 7 submm galaxies in the SA22 structure, making this region the richest association of these intensely active galaxies. Finally we suggest that Lya haloes may be a common feature of the submm population in general, and have an important role in the heating and enrichment of the intergalactic medium.