PI: Jason X. Prochaska, Carnegie Observatories, email@example.com
Address: 813 Santa Barbara St., Pasadena, CA 91101, USA
CoI: Todd Tripp, Princeton University
CoI: Hsiao-Wen Chen, Carnegie Observatories
CoI: John Mulchaey, Carnegie Observatories
Title: Surveying the Origin of O VI Gas at Low Redshift
Abstract: A comparison of the baryonic mass density inferred from BBN with a census of visible baryonic components (i.e. galaxies, HI gas) at the present epoch indicates a significant fraction of the universe's baryons are hidden in a dark component. Theoretical investigations into these missing bayons 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 this proposal is to determine if this \ovi gas arises in galactic halos, the intragroup or intracluster medium, the low density 'cosmic web' which connects collapsed objects, or a different region of the universe altogether. We are currently pursuing a program to search for galaxies associated with \ovi absorbers at low redshift (z < 0.5). To accomplish this project, we will obtain deep UBVRI images of the galaxies in four fields surrounding quasars surveyed for \ovi\ absorption. This dataset will provide accurate photometric redshifts of the z<0.5 galaxies with L > L^*/10 and will reveal their physical characteristics. 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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