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Title

H-2-bearing damped Lyman-alpha systems as tracers of cosmological chemical evolution

Author(s)

Murphy, Michael T.;  Curran, Stephen J.;  Webb, J. K.

Abstract

The chemical abundances in damped Lyman-alpha systems (DLAs) show more than 2 orders of magnitude variation at a given epoch, possibly because DLAs arise in a wide variety of host galaxies. This could significantly bias estimates of chemical evolution. We explore the possibility that DLAs in which H-2 absorption is detected may trace cosmological chemical evolution more reliably since they may comprise a narrower set of physical conditions. The 9 known H-2 absorption systems support this hypothesis: metallicity exhibits a faster, more well-defined evolution with redshift than in the general DLA population. The dust-depletion factor and, particularly, H-2 molecular fraction also show rapid increases with decreasing redshift. We comment on possible observational selection effects which may bias this evolution. Larger samples of H-2-bearing DLAs are clearly required and may constrain evolution of the UV background and DLA galaxy host type with redshift.

Publication type

Conference paper

Source

Recycling intergalactic and interstellar matter: proceedings of the 217th Symposium of the International Astronomical Union held during the IAU General Assembly XXV, Sydney, Australia, 14-17 July 2003 / Pierre-Alain Duc, Jonathan Braine and Elias Brinks (eds.), pp. 252-257

Publication year

2004

Keyword(s)

Column density;  Depletion pattern;  Galaxies;  Gas;  HE-0515-4414;  Kinematics;  Metallicity evolution;  Molecular-hydrogen abundance;  Protogalaxies;  Redshift

Publisher

Astronomical Society of the Pacific

ISSN

0074-1809 (series ISSN)

ISBN

1583811664

Copyright

Copyright © 2004 Astronomical Society of the Pacific. The accepted manuscript is reproduced in accordance with the copyright policy of the publisher.

Full text

Peer reviewed