Letter to the Editor First detections of FIRBACK sources with SCUBA

The FIRBACK (Far InfraRed BACKground) survey represents the deepest extensive 170 μm images obtained by the ISO satellite. The sources detected comprise about 10% of the Cosmic IR Background (CIB) seen by COBE, and, importantly, were observed at a wavelength near the peak of the CIB. Detailed follow-up of these sources should help pin down the redshifts, Hubble types, and other properties of the galaxies which constitute this background. We have used the Submillimetre Common-User Bolometer Array (SCUBA) instrument on the James Clerk Maxwell Telescope (JCMT) to search for sub-mm emission from a sample of 10 galaxies which are bright at 170 μm and for which we had accurate radio positions. Statistically we detect this sample at both 450 μm (∼ 4σ) and 850 μm (∼ 7σ); individual objects are convincingly detected in four cases at 850 μm, and one case at 450 μm. Fits to simple spectral energy distributions suggest a range of low to moderate redshifts, perhaps z = 0–1.5 for this FIRBACK sub-sample.