Continuum Observations of the High-Redshift Universe at Sub-millimetre Wavelengths

Abstract

New bolometer arrays operating on the world's largest sub-mm and mm telescopes offer a unique view of the high-redshift universe with unprecedented sensitivity. Recent sub-millimetre continuum studies show that the host galaxies of many luminous high-redshift AGN (radio galaxies and radio-quiet quasars) radiate strongly at rest-frame far-infrared wavelengths and thus contain substantial quantities of dust. In the majority of these high-redshift AGN-hosts, the inferred star formation is proceeding at a rate comparable to that found in local, interacting ultra-luminous FIR galaxies. This level of activity is an order of magnitude greater than the more modest star-formation rates apparently displayed by the recently-discovered Lyman-limit galaxies at z ~ 3, which have been argued to represent the era of spheroid formation (although the degree to which the effects of reddening by dust grains may have biased the interpretation of these optical/UV studies of high-z galaxies has yet to be properly determined). However, it is too early to say whether such bright FIR emission is a feature of all massive galaxies at z > 3, or whether it is in fact confined to the hosts of the most luminous AGN. In this paper we review the current status of cosmological observations at sub-mm and mm wavelengths, highlighting our own recent SCUBA observations of high-redshift radio galaxies. We also explain how observations over the next few years should allow the true level of star-formation activity in the high-z universe to be properly quantified, and we provide example predictions for the first deep sub-millimetre survey (of the Hubble Deep Field), which we and our colleagues are currently undertaking with SCUBA at the JCMT.