OBSERVATIONS OF HIGH-REDSHIFT OBJECTS AT SUBMILLIMETER WAVELENGTHS

We have used the James Clerk Maxwell Telescope to search for millimetre- and submillimetre-wave emission from the host galaxies of nine QSOs having redshifts greater than 4. Strong continuum emission was detected from one of these, BR1202-0725 (z = 4.69), in each of the 1100-, 800- and 450-mum atmospheric windows. The spectral index between 1100 and 800 mum is greater than 2, which strongly suggests that the emission is from dust. The continuum spectrum is fitted best by a dust temperature of 53 K, although values as high as 100 K cannot be excluded. The observed submillimetre fluxes are close to those that would be observed from an object like IRAS 10214 + 4724 if it were shifted to a redshift of 4.69 (assuming OMEGA = 1). Two other sources were detected at statistically significant levels: BR1033 - 0327, another radio-quiet QSO, and GB1508 + 5714, a radio-loud QSO. A search for C+ (lambda = 158 mum) fine emission from BR1202 - 0725 failed to detect a line. A line 250 km s-1 wide should have been seen if it had a line-to-continuum ratio greater than about 1.