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Proposal Information for 2010A-0238


PI: Dr. John S. Mulchaey, Carnegie Observatories, mulchaey@obs.carnegiescience.edu
Address: 813 Santa Barbara St., Pasadena, CA 91101, USA

CoI: Dr. Hsiao-Wen Chen, University of Chicago

Title: Casting Light on the Warm-Hot Intergalactic Medium

Abstract: It has been known for over a decade that the observed baryons in the local universe fall far short of the amount required by cosmological models. Simulations suggest that the bulk of the so-called \lq\lq missing baryons\rq\rq is contained in the shock-heated warm-hot intergalactic medium (WHIM). Despite considerable effort, direct detection of the WHIM has proved difficult. Perhaps the best probe of the WHIM is spectroscopic observations of high ionization species in the spectra of background QSOs. In particular, the ultraviolet lines of Ne VIII(lambda)(lambda)770.5,780.3 are expected to be a powerful tracer of hot collisionally ionized gas. Unfortunately, only two Ne VIII absorption systems have been found to date because of the limits of UV spectrographs. The successful installation of COS on HST should soon change this situation. As demonstrated by our recent study of the Ne VIII absorber toward HE0226-4110, deep spectroscopic surveys of galaxies in the vicinity of absorbers are required to distinguish between the WHIM and other possible origins for the warm gas. Unfortunately, such studies will be difficult for Ne VIII systems discovered with COS because they will all be at z > 0.5. However, there is one additional lower redshift Ne VIII system discovered by FUSE for which the galactic environment has not been quantified. Here, we propose to use GMOS on Gemini north to complete a galaxy survey around this absorber to better understand Ne VIII as a probe of the WHIM.


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