Cosmological evolution of heavy-element and H2 abundances
Abstract
Spectroscopic observations of distant quasars have resulted in the detection of molecular hydrogen in intervening damped Lyman α absorption clouds (DLAs). We use observations compiled from different experimental groups to show that the molecular hydrogen abundance exhibits a dramatic increase over a cosmological time period corresponding to 13 to 24 per cent of the age of the Universe. We also tentatively show that the heavy-element abundances in the same gas clouds exhibit a faster and more well-defined cosmological evolution compared with the general DLA population over the same time baseline. We argue that this latter point is unsurprising, because the general DLA population arises in a wide variety of galaxy types and environments, and thus a spans broad range of ISM gas-phases and abundances at the same cosmic time. DLAs exhibiting H2 absorption may therefore circumvent this problem, efficiently identifying a narrower class of objects, and provide a more sensitive probe of cosmological chemical evolution.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- June 2004
- DOI:
- 10.1111/j.1365-2966.2004.07958.x
- arXiv:
- arXiv:astro-ph/0311357
- Bibcode:
- 2004MNRAS.351L..24C
- Keywords:
-
- line: identification;
- ISM: molecules;
- Galaxy: abundances;
- intergalactic medium;
- quasars: absorption lines;
- ultraviolet: general;
- Astrophysics
- E-Print:
- 5 pages, 2 figures. Accepted by MNRAS Letters. v2: Added table summarizing H2-bearing DLA properties, added figure showing [Fe/H] vs. redshift, added more discussion