Molecular Hydrogen in high redshift Damped Lyman-α systems

Author: Petitjean Patrick  

Publisher: Springer Publishing Company

ISSN: 0004-640X

Source: Astrophysics and Space Science, Vol.281, Iss.1-2, 2002-07, pp. : 467-470

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Abstract

I describe briefly the status of an ongoing mini-survey for molecular hydrogen in high-redshift Damped Lyman-α systems using UVES at the VLT. H2 is detected in about 30% of the cases. When H2 is not detected the molecular fraction f = 2N(H2)/(2N(H2)+N(HI) is smaller than 10-5. Therefore, most of the DLA systems arise in warm (T > 3000 K) and diffuse neutral gas embedded in a strong UV flux. The very recent detection of HD molecules in a Damped Lyman-α system at z abs = 2.337 demonstrates the possibility to discuss the high redshift chemistry.