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Astron. Astrophys. 349, 363-368 (1999)


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Dust and CO lines in high redshift quasars

S. Guilloteau 1, A. Omont 2, P. Cox 3, R.G. McMahon 4 and P. Petitjean 2

1 IRAM, 300 rue de la Piscine, F-38406 Saint Martin d'Hères Cedex, France
2 Institut d'Astrophysique de Paris, CNRS, 98bis Bd Arago, F-75014 Paris, France
3 Institut d'Astrophysique Spatiale, Université Paris XI, F-91405 Orsay Cedex, France
4 Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK

Received 18 March 1999 / Accepted 16 June 1999

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 [FORMULA] 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 [FORMULA] from the broad-band bolometer fluxes, consistent with an average spectral index of [FORMULA] 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 [FORMULA] km s-1, we obtain typical upper limits of [FORMULA] Jy km s-1 at the [FORMULA] level in the frequency (redshift) range searched. We report a tentative ([FORMULA]) 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 [FORMULA]. After BR 1202-0725 at [FORMULA] (Otha et al. 1996, Omont et al. 1996a), and BRI 1335-0417 at [FORMULA] (Guilloteau et al. 1997), this is the third detection of CO at [FORMULA]. The velocity-integrated CO(5-4) line flux is [FORMULA], with a linewidth of [FORMULA]. The 1.35 mm (250 [FORMULA] rest wavelength) dust continuum flux density is 2.23[FORMULA]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.

Key words: galaxies: formation – galaxies: quasars: emission lines – galaxies: quasars: individual: BRI 0952-0115 – galaxies: quasars: individual: Q 1230+1627B – cosmology: observations – cosmology: early Universe

Send offprint requests to: S. Guilloteau

© European Southern Observatory (ESO) 1999

Online publication: September 2, 1999

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