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H2-Bearing Damped Lyman-α Systems as Tracers of Cosmological Chemical Evolution

Published online by Cambridge University Press:  26 May 2016

M. T. Murphy ,
S. J. Curran  and
J. K. Webb
M. T. Murphy
Affiliation:
Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
S. J. Curran
Affiliation:
School of Physics, University of New South Wales, Sydney 2052, Australia
J. K. Webb
Affiliation:
School of Physics, University of New South Wales, Sydney 2052, Australia

Abstract

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The chemical abundances in damped Lyman-α 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 H2 absorption is detected may trace cosmological chemical evolution more reliably since they may comprise a narrower set of physical conditions. The 9 known H2 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, H2 molecular fraction also show rapid increases with decreasing redshift. We comment on possible observational selection effects which may bias this evolution. Larger samples of H2-bearing DLAs are clearly required and may constrain evolution of the UV background and DLA galaxy host type with redshift.

Type
Part 2. Origin
Information
Symposium - International Astronomical Union , Volume 217: Recycling Intergalactic and Interslettar Matter , 2004 , pp. 252 - 257
Copyright
Copyright © Astronomical Society of the Pacific 2004 

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