Atomic carbon in PSS 2322 + 1944 , a quasar at redshift 4 . 12 ⋆

We report the detection of the 3 P1→ 3 P0 fine-structure line of neutral carbon in the z = 4.12 quasar PSS 2322+1944, obtained at the IRAM Plateau de Bure interferometer. The [Ci] 3 P1 − 3 P0 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 0.81 ± 0.12 Jy km s −1. Assuming an excitation temperature of 43 K (equal to the dust temperature), we derive a mass of neutral carbon (corrected for magnification) of MCI ≈ 1.2 × 10 7 M⊙. 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 + .