Spectral energy distribution of submillimeter sources

The submillimeter universe has now been explored with the Submillimeter Com mon User Bolometer Array (SCUBA) camera on the James Clerk Maxwell Telescop e, and claims have been made to the presence of a new population of optical ly unidentified starforming dusty galaxies at high redshifts. An alternativ e interpretation of the submillimeter (submm) emission from these sources, however, is that their far infrared emission is due to the presence of an a ctive galactic nucleus (AGN) enshrouded by dust. Using examples of submm so urces, selected primarily due to the availability of multiwavelength observ ations, we investigate whether the spectral energy distribution (SED) selec ted sources is consistent with either the dusty starforming or dusty AGN sc enarios. Among these sources, we find that the SED of HDF850.4, one of the sources detected in the Hubble Deep Field (HDF), and CFRS14F, one of the so urces in the Canada France Redshift Survey Fields, are fully consistent wit h the dusty starformation hypothesis, while the SED of APM 08279+5255 is co nsistent with a dusty AGN. For some submm sources, it is suggested that obs ervations at rest wavelengths between similar to 1 mu m and 100 mu m may be needed to differentiate between the dusty starformation and dusty AGN scen arios. We discuss implications of our results for the interpretation of sub mm sources and suggest that dusty AGNs can contribute up to similar to 30% of the submm source counts. However, an exact observational determination o n the ratio of dusty star-forming to dusty AGN contribution to submm counts require detailed followup observations of a flux limited source catalog, b eyond what is currently available. (C) 1999 Elsevier Science B.V. All right s reserved.