Atomic Carbon in APM 08279+5255 at z = 3.91

We present a detection of [C I] ³P₁-³P₀ emission in the lensed quasar APM 08279+5255 at z=3.91 using the IRAM Plateau de Bure interferometer. The [C I] line velocity and width are similar to the values of previously detected high-J CO and HCN lines in this source, suggesting that the emission from all of these species arises from the same region. The apparent luminosity of the [C I] line is L^'_CI=(3.1+/-0.4)×10¹⁰ K km s^-1 pc², which implies a neutral carbon mass M_CI=(4.4+/-0.6)m^-1×10⁷ M_solar, where m is the lensing magnification factor. The [C I] line luminosity is consistent with the large molecular gas mass inferred from the nuclear CO line luminosity (~10¹¹m^-1 M_solar). We also present an upper limit on the H₂O 1₁₀-1₀₁ line luminosity in APM 08279+5255 of L^'_H2O<1.8×10¹⁰ K km s^-1 pc² (3 σ).

Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).