NOAO >   Observing Info >   Approved Programs >   2005A-0139

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Proposal Information for 2005A-0139


PI: Jason X. Prochaska, UCO/Lick Observatory, xavier@ucolick.org
Address: Astronomy Department, UC Santa Cruz, Santa Cruz, CA 95064, USA

CoI: Todd Tripp, University of Massachusetts
CoI: Romeel Dave, Steward Observatory
CoI: John Mulchaey, Carnegie Observatories
CoI: Hsiao-Wen Chen, MIT

Title: Surveying the Origin of O VI Gas at Low Redshift

Abstract: A comparison of the baryonic mass density inferred from BBN and the CMB with a census of visible baryonic components at the present epoch indicates a significant fraction of the universe's baryons are hidden in a dark component. Theoretical investigations the majority of 'missing' baryons lie in a hot (T ~ 10^5-7 K), low density medium which can be efficiently detected through \ovi absorption. More importantly, recent STIS+FUSE surveys for \ovi are consistent with this gas comprising a significant fraction of the missing baryons. Establishing the physical nature of these \ovi absorbers directly impacts our understanding of the distribution of baryons in the universe. The principal goal of our program is to determine if this \ovi gas arises in galactic halos, the intragroup or intracluster medium, the low density 'cosmic web', or a different region of the universe altogether. We are pursuing an observational program to search for galaxies associated with \ovi absorbers at low redshift (z < 0.5). To accomplish this project, we require deep UBVRI images in fields surrounding quasars surveyed for \ovi absorption. This dataset will provide precise photometric redshifts of z<0.5 galaxies with L > L^*/10 and measures of color and morphology. Ultimately, we will use the photometric redshifts to efficiently pre-select galaxies for spectroscopy on multi-slit spectrographs. By correlating the galaxy redshifts against the \ovi absorption lines and comparing directly with cosmological simulations, we will establish the origin of the \ovi gas.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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