Redshifted molecular absorption systems towards PKS1830-211 and B0218+357: submillimeter CO, CI and H2O data

Preprint

19 August 1997

preprint
Published by arXiv in arXiv

https://doi.org/10.48550/arXiv.astro-ph/9708175

Abstract

We have detected the J=4-3 rotational transition of 12CO in absorption at z=0.89 towards the quasar PKS1830-211, but not the 12CO 5-4 or the 3P1-3P0 fine structure line of neutral carbon. The intervening molecular medium thus has a total 12CO column density of N(CO)~2x10^18 cm^-2, which corresponds to the large column density of molecular hydrogen of N(H2)=2.5x10^22 cm^-2 and a reddening of Av=25 magnitudes. The 12CO excitation temperature is low, below 15 K. Comparison with the molecular absorption results of Wiklind and Combes (1996) shows that the absorbing material has similar molecular abundances to Galactic dark clouds. We find an upper limit for atomic carbon of N(CI)2x10^22 cm^-2, corresponding to a reddening >20 magnitudes.

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Version 1, 1997-08-19, ArXiv
Published version: The Astrophysical Journal, 488 (1), L31.

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