NOAO >   Observing Info >   Approved Programs >   2003A-0009

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Proposal Information for 2003A-0009


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

CoI: Todd Tripp, Princeton University
CoI: John Mulchaey, Carnegie Observatories
CoI: Hsiao-Wen Chen, MIT
CoI: Ben Weiner, UCO/Lick Observatory

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 into these missing baryons suggest the majority 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, therefore, may have great impact on 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 currently 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 of the galaxies 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 utilize the photometric redshifts to efficiently pre-select galaxies for follow-up spectroscopy on multi- slit spectrographs. By correlating the photometric and spectroscopy galaxy redshifts against the \ovi absorption lines and comparing directly with detailed cosmological simulations, we will establish the origin of the \ovi gas.


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