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Paper: H_2 and C I in Damped LY alpha Quasar Absorbers at Intermediate and High Redshifts
Volume: 156, Highly Redshifted Radio Lines
Page: 121
Authors: Ge, J.; Bechtold, J.
Abstract: We report results from our survey for H_2 and C I absorption in damped Ly alpha quasar absorbers (DLA) at redshifts z = 0.7 to 2.9. Strong H_2 absorption lines have been detected in the z = 1.97 DLA toward Q 0013-004 and z = 2.34 DLA toward Q 1232+0815. We show that the kinetic temperatures, rotational excitation temperatures and hydrogen particle densities in these DLAs are similar to those in Milky Way diffuse clouds with similar fractional H_2 abundance. The derived UV radiation field strength is about a factor of ten above the Milky Way average value, indicating the DLAs either are close to star formation regions or have high global star formation rates. We have also derived upper limits for the rest of the DLAs which show no H_2 absorption. Together with previous results, we find a strong correlation between the fractional H_2 abundance and relative heavy element depletion. The derived excitation temperature of the fine-structure of C I, associated with the DLAs showing H_2 absorption, is used to measure the cosmic microwave background radiation (CMBR) temperatures to test the validity of the Big Bang cosmology at high redshifts. So far, the results are consistent with the prediction.
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