Dust and CO lines in high redshift quasars
Abstract
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 ~ 3.5 within 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 3 sigma level in the frequency (redshift) range searched. We report a tentative (3 sigma ) 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 microns 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.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 1999
- Bibcode:
- 1999A&A...349..363G
- Keywords:
-
- GALAXIES: FORMATION;
- GALAXIES: QUASARS: EMISSION LINES;
- GALAXIES: QUASARS: INDIVIDUAL: BRI 0952-0115;
- GALAXIES: QUASARS: INDIVIDUAL: Q 1230+1627B;
- COSMOLOGY: OBSERVATIONS;
- COSMOLOGY: EARLY UNIVERSE