Redshifted molecular absorption systems toward PKS 1830-211 AND B0218+357: submillimeter CO, C1, and H2O data

We have detected the J = 4 <-- 3 rotational transition of (CO)-C-12 in absorption at z = 0.89 toward the quasar PKS 1830-211, but not the (CO)-C-12 (5<--4) or the P-3(1)<--P-3(0) fine-structure line of neutral carbon. The intervening molecular medium thus has a total (CO)-C-12 column density of 10(18) cm(-2)less than or equal to N(CO)less than or equal to 5 x 10(18) cm(-2) with a most likely value of N(CO) similar or equal to 2 x 10(18), which corresponds to the large column density of molecular hydrogen of N(H-2) = 2.5 x 10(22) cm(-2) and a reddening of A(F) = 25 mag. The (CO)-C-12 excitation temperature is low, below 15 K. Comparison with existing molecular absorption results shows that the absorbing material has molecular abundances similar to Galactic dark clouds. We find an upper limit for atomic carbon of N(C I) less than or equal to 10(18) cm(-2), which again would be the case for most Galactic dark clouds. We also report new observations of the absorbing system toward B0218+357 at z = 0.68. We have tentatively detected the (CO)-C-13 (4<--3) line, but for H2O, although a feature is seen at the correct velocity, because of the inadequate signal-to-noise ratio we report only an upper limit for the fundamental line of ortho-water vapor. The tentative detection of the (CO)-C-13 J = 4<--3 line implies that the (CO)-C-13 excitation temperature is lower than 20 K and the column density is fairly large, 4 x 10(16) cm(-2) less than or equal to N(CO13)less than or equal to 2.2 x 10(17) cm(-2), with a likely value of N(CO13) similar or equal to 10(17) cm(-2), giving rise to saturated absorption in the J = 2<--1 transition. The total column density of molecular gas is again large in this source, N(H-2)greater than or equal to 2 x 10(22) cm(-2), which corresponds to a reddening larger than 20 mag.