Gas and dust in the Cloverleaf quasar at redshift 2.5

We observed the upper fine structure line of neutral carbon, \ctwo (nu_rest = 809 GHz), the \cco line (nu_rest = 345 GHz) and the 1.2 mm continuum emission from H1413+117 (Cloverleaf quasar, z=2.5) using the IRAM interferometer. Together with the detection of the lower fine structure line (Barvainis \etal 1997), the Cloverleaf quasar is now only the second extragalactic system, besides M 82, where both carbon lines have convincingly been detected. Our analysis shows that the carbon lines are optically thin and have an excitation temperature of \tex ~ 30 K. CO is subthermally excited and the observed line luminosity ratios are consistent with \nhh ~ 10^3-4 cm^-3 at \tkin = 30-50 K. Using three independent methods (\ci, dust, CO) we derive a total molecular gas mass (corrected for magnification) of M(hh ) ~ 1.2 +/- 0.3 x 10¹⁰ msol . Our observations suggest that the molecular disk extends beyond the region seen in CO(7-6) to a zone of more moderately excited molecular gas that dominates the global emission in \ci and the low J CO lines.