H_2-bearing damped Lyman-alpha systems as tracers of cosmological chemical evolution
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.
Keywords
Cite
@article{arxiv.astro-ph/0310409,
title = {H_2-bearing damped Lyman-alpha systems as tracers of cosmological chemical evolution},
author = {M. T. Murphy and S. J. Curran and J. K. Webb},
journal= {arXiv preprint arXiv:astro-ph/0310409},
year = {2007}
}
Comments
6 pages, 1 figure, 1 table, v2: updated references, corrected typos, to appear in Recycling intergalactic and interstellar matter, IAU Symposium series, Vol. 217, 2004, edited by P.-A. Duc, J. Braine, E. Brinks