AAS 197, January 2001
Session 20. Galaxy Formation and Chemical Evolution
Oral, Monday, January 8, 2001, 10:30am-12:00noon, San Diego

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[20.04] The Chemical Evolution of the Universe

A. C. Baker, G. P. Mathlin, D. K. Churches, M. G. Edmunds (Dept. Physics and Astronomy, Cardiff)

We have constructed a simple, robust model of the chemical evolution of galaxies from high to low redshift, and applied it to published observations of damped Lyman-alpha quasar absorption line systems (DLAs). The elementary 'monolithic collapse' model assumes quiescent star formation and isolated galaxies (no interactions, mergers or gas flows). These calculations appear in Mathlin, Baker, Churches and Edmunds (2000) (astro-ph/0009226, MNRAS in press), where we also consider the influence of dust and chemical gradients in the galaxies, and hence explore the selection effects in quasar surveys. We fit individual DLA systems to predict observable properties of the absorbing galaxies, and also indicate the expected redshift behaviour of chemical element ratios involving nucleosynthetic time delays. Many DLA absorber galaxies are rather faint and close to the quasar line-of-sight, requiring at least eight-metre class telescopes, and adaptive optics to be detected even in the near-IR.

Despite its simplicity, our elementary model gives a good account of the distribution and evolution of the metallicity and column density of DLAs, and of the evolution of the global star formation rate and gas density below redshifts z ~3. However, from the comparison of our model with observations, star formation rates at higher redshifts (z > 3) are clearly enhanced in the real Universe. Galaxy interactions and mergers, and gas flows very probably play a major role.

We are now engaged in a 'two pronged' attack on the questions raised in Mathlin et al. (2000). As part of the QuickStart Gemini North observations programme, we are acquiring deep, high spatial resolution Hopuka'a/QUIRC K band observations of DLA quasars studied by Mathlin et al. (2000). We are also incorporating merger-induced starburst activity into our chemical evolution models. I will present our latest results from Gemini North, and their interpretation in our revised theoretical framework.

Research funded by the UK Particle Physics and Astronomy Research Council, and the Department of Physics and Astronomy of Cardiff University.

If you would like more information about this abstract, please follow the link to http://www.astro.cf.ac.uk/groups/chemevol/. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

The author(s) of this abstract have provided an email address for comments about the abstract: a.baker@astro.cf.ac.uk

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