The Submillimetre Universe

Submillimetre continuum radiation allows us to probe cold objects, particularly the earliest, dusty phases of star formation, high-redshift galaxies and circumstellar disks. The submillimetre window gives a unique view of the physical and dynamical conditions in the neutral and molecular interstellar medium. In the next decade a combination of wide-field surveys with single-dish telescopes and targeted follow-up with ALMA and other facilities should enable rapid progress in answering questions about the origins of planetary systems, stars and galaxies. Subject headings: Submm – Universe 1. THE SUBMM WINDOW The sub-millimetre (hereafter ‘submm’) waveband is usually defined to stretch from 200µm to 1mm. There are strong physical reasons why this range of wavelengths is of particular astronomical interest, reasons which are partly shared with the neighbouring far-IR and mm bands. In accord with the ‘Origins’ theme of the 2000 Canadian Long Range Plan, the earliest stages of planet, star and galaxy formation are most directly amenable to study at submm wavelengths. The youngest systems in the Universe tend to be shrouded in dust, which absorbs shorter wavelength radiation and re-emits at hundreds of microns (Fig. 1). So to study cold systems, including the early stages of star formation, debris disks in nearby stellar systems and high redshift star-forming galaxies, one naturally turns to submm wavelengths, where the opacity is low and thermal emission is being probed directly.