NOAO >   Observing Info >   Approved Programs >   2011B-0587

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Proposal Information for 2011B-0587


PI: Debopam Som, Univ. of South Carolina, som@physics.sc.edu
Address: Dept. of Physics and Astronomy, 712 Main St., Columbia, SC 29208, USA

CoI: Varsha P. Kulkarni, University of South Carolina
CoI: Joseph Meiring, University of Massachusetts
CoI: James T. Lauroesch, University of Louisville
CoI: Celine Peroux, Obs. Astron. de Marseille-Provence
CoI: Pushpa Khare, Utkal University
CoI: Donald G. York, University of Chicago
CoI: Monique C. Aller, University of South Carolina

Title: Probing Chemical Enrichment and Star Formation in Galaxies Using Sub- Damped Lyman-alpha Quasar Absorbers

Abstract: Damped Lyman-(alpha) (DLA) absorbers in quasar spectra have historically been used to probe neutral gas content of the universe, but show low metallicity at all redshifts, and evolve more slowly than model predictions. Surprisingly, our recent work finds the metallicty in sub- DLAs to be higher and evolving faster than DLAs at 0.7 < z < 1.5. Furthermore, at these redshifts, the more metal-rich sub-DLAs usually show higher gas velocity dispersions. These findings, together with differences in [Mn/Fe] vs. metallicity trends, suggest different stellar populations for DLAs and sub-DLAs, possibly illustrating mass- downsizing in galaxies. Here, we propose to test these ideas as follows: (1) We will increase the sub-DLA metallicity samples at z < 0.7 and z > 3 by factors of 2 and > 5, respectively, and determine metallicity evolution more accurately; (2) obtain significantly better estimates of trends in [Mn/Fe] and [Si/Fe] vs. metallicity in sub-DLAs to test whether they imply an early stellar population; (3) constrain SFRs in high-z sub-DLAs by measuring C II* (lambda) 1335.7 absorption; (4) search for H_2 and CO absorption in high-z sub-DLAs, to understand how molecular content relates to metallicity and dust content. Our data will provide fresh insights into the nature of sub-DLAs, their relationship with DLAs, and the implications for galaxy evolution.


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