Dust and CO lines in high redshift quasars

We report the results of a systematic search for redshifted rotational lines of CO and dust emission towards a sample of 9 high redshift radio quiet quasars using the IRAM Plateau de Bure interferometer. Dust emission at ∼ 1.35 mm has been found in 5 out of the 9 objects. These results confirm the corresponding previous detections with the MPIfR bolometer at the 30-m. No 3 mm continuum was detected in any source. The flux densities measured at 1.35 mm with the interferometer are systematically smaller by ∼ 30% from the broad-band bolometer fluxes, consistent with an average spectral index of ∼ 3.5within the calibration uncertainty. In parallel, searches for CO in significant redshift ranges were performed for 8 of the above sources. 6 sources were not detected. Assuming a line width of ≤ 450 km s−1, we obtain typical upper limits of ∼ 0.4–0.5 Jy km s−1 at the 3σ level in the frequency (redshift) range searched. We report a tentative (3σ) detection of the J=3-2 line of CO in Q 1230+1627B, and a unambigous detection of the J=5-4 CO line in the gravitationally lensed radio quiet quasar BRI 0952−0115 at a redshift of z = 4.43. After BR 1202−0725 at z = 4.69 (Otha et al. 1996, Omont et al. 1996a), and BRI 1335−0417 at z = 4.41 (Guilloteau et al. 1997), this is the third detection of CO at z > 4. The velocity-integrated CO(5-4) line flux is 0.91 ± 0.11 Jy km s−1, with a linewidth of 230 ± 30 km s−1. The 1.35 mm (250 μm rest wavelength) dust continuum flux density is 2.23±0.51 mJy, in agreement with previous measurements at 1.25 mm at the 30-m IRAM telescope. The ratio of the CO to 1.35 mm continuum flux is comparable to that of BRI 1335−0417 and 2-3 times larger than for BR 1202−0725. The angular resolution of the observation is not high enough to give evidence of any extension of the 1.35 mm continuum and 3 mm CO emission.