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Astron. Astrophys. 360, 846-852 (2000)

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Constraints on the physical properties of the damped Ly[FORMULA] system of Q0000-2619 at z = 3.054

G. Giardino and F. Favata

Astrophysics Division - Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands

Received 29 March 2000 / Accepted 16 June 2000


We present the detection of C II and C II * absorption in the [FORMULA] damped Ly[FORMULA] system toward Q0000-2619. The derived population ratio implies a fine structure excitation temperature between 19.6 and 21.6 K. The upper value sets a strict upper limit on the CMB temperature at this redshift, which is consistent with the predicted value of 11.05 K from standard cosmology. Under the assumptions of an ionization degree ranging from 0 to 10%, a gas kinetic temperature between 100 and 10 000 K and a UV field with a Milky Way spectrum, the density of the absorber is constrained to be between 0.7 and 40 cm-3 and the H-ionizing flux between 1 and 80 times the intensity of the Galactic UV field. If the damped Ly[FORMULA] system is assumed to be homogeneous, the implication is that its size in the direction of the line of sight must be between 1 and 100 pc.

Key words: cosmology: cosmic microwave background – galaxies: intergalactic medium – galaxies: quasars: absorption lines – galaxies: quasars: individual: Q0000-2619

Send offprint requests to: G. Giardino (ggiardin@astro.estec.esa.nl)

© European Southern Observatory (ESO) 2000

Online publication: August 23, 2000