1999MNRAS.305...61T

A major recent development in extragalactic astronomy has been the discovery of a population of galaxies that is luminous at submillimetre wavelengths. Estimates of their spectral energy distributions suggest that these galaxies are the high-redshift analogues of the ultraluminous infrared galaxies (ULIRGs) observed locally. Here we investigate the implications for the galaxy formation problem if this is indeed the case. We identify plausible (but non-unique) redshift-dependent galaxy luminosity functions that are consistent with both source counts at 2800, 850, 450 and 175 µ m and far-infrared background radiation intensities at 850, 240 and 140 µ m. In all our models, most of the submillimetre-luminous sources are distant galaxies with high bolometric luminosities ≥ 10¹² L_☉. As for many local ULIRGs, it is not possible to determine whether these luminous galaxies are powered by starbursts, like the local galaxy Arp 220, or by active galactic nuclei (AGN), like the local galaxy Markarian 231. We investigate both possibilities. If the submillimetre-luminous galaxies are all starbursts, then we predict that the fraction of the cosmic star formation rate in these objects is large, but does not necessarily dominate the star formation rate of the Universe – the Madau plot – at any redshift. Only a few per cent by mass of the present-epoch spheroidal stellar population would have been formed in such a population of star-forming galaxies, consistent with the constraints on the number of galaxies with old stellar populations in the field at low and intermediate redshifts derived from K-band surveys. If the submillimetre-luminous galaxies are all powered by AGN, then the comoving density of supermassive black holes on to which material is accreting at high redshift probably equals no more than a few per cent of the local density of massive dark objects.