NOAO >   Observing Info >   Approved Programs >   2001A-0151

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Proposal Information for 2001A-0151


PI: John T. Stocke, University of Colorado, stocke@casa.colorado.edu
Address: CB 389, Boulder, CO 80309, USA

CoI: Kevin M. McLin, University of Colorado
CoI: Steven V. Penton, University of Colorado
CoI: J. Michael Shull, University of Colorado

Title: Local Lyman (alpha) Forest: Tracing Large-Scale Structure with Absorbers and Galaxies

Abstract: We propose to use the WIYN+HYDRA to conduct a galaxy redshift survey to B\le19 in the vicinity of very local \rm (cz \lesssim 7,500 km s^-1)\: Ly(alpha) clouds found in the spectra of four very bright AGN, comprising two close pairs, observed or to be observed with HST. Our previous WIYN + HYDRA results have helped prove that these very low column density (log N(H I)<14.5) clouds are intergalactic, i.e., not associated with individual galaxies. Current estimates suggest that, while virtually all of the baryons (\Omega_b >=80%) in the Universe were in the IGM at high z (>=3), at least 20% of the baryons still reside in these clouds today. The primary purpose of the current proposal is to search for faint galaxies in the vicinity of two close pairs of QSO sightlines to trace out the large-scale structure in both galaxies and absorbing gas, \bf for the first time. Preliminary work with WIYN + HYDRA and a multi-object spectrograph at the Las Campanas 100" finds evidence in one of these sightlines for a large-scale structure filament at cz=1000-2000 km s^-1, traced by 7 Ly(alpha) absorbers and 8 known galaxies. These observations will allow a more detailed interpretation of common pairs of absorbers found in these sightlines than is possible at higher redshift. These observations will provide a much more secure size for Ly(alpha) clouds and so a much more secure value for \Omega_b in the IGM.


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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