Letter to the Editor

Atomic carbon in PSS 2322+1944, a quasar at redshift ^*

¹ IRAM, 300 rue de la Piscine, 38406 St-Martin-d'Hères, France e-mail: pety@iram.fr
² LERMA, Observatoire de Paris, 75014 Paris, France
³ Institut d'Astrophysique Spatiale, Université de Paris Sud, 91405 Orsay Cedex, France
⁴ Institut d'Astrophysique de Paris, CNRS and Université de Paris VI, 98bis Bd. Arago, 75014 Paris, France
⁵ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁶ National Radio Astronomy Observatory, PO Box, Socorro, NM 87801, USA

Received: 22 September 2004
Accepted: 30 October 2004

Abstract

We report the detection of the fine-structure line of neutral carbon in the quasar PSS 2322+1944, obtained at the IRAM Plateau de Bure interferometer. The [Ci] line is detected with a signal-to-noise ratio of ~6 with a peak intensity of ≈2.5 mJy and a velocity-integrated line flux of . Assuming an excitation temperature of 43 K (equal to the dust temperature), we derive a mass of neutral carbon (corrected for magnification) of . In PSS 2322+1944, the cooling due to C is about 6 times smaller than for CO, whereas the CO and C cooling represents ≈10^-4 of the far-infrared continuum and more than half of the cooling due to C⁺.