Atomic carbon in PSS 2322+1944, a quasar at redshift 4.12

We report the detection of the 3 P 1 → 3 P 0 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 P 1 - 3 P 0 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 M Cl 1.2 x 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 + .