Observations of high-redshift objects at submillimetre wavelengths

Abstract

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-μm atmospheric windows. The spectral index between 1100 and 800 microns 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 Ω = 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+ (λ = 158 μm) line 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.