NOAO >   Observing Info >   Approved Programs >   2003B-0089

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Proposal Information for 2003B-0089


PI: David V. Bowen, Princeton Observatory, dvb@astro.princeton.edu
Address: Astrophysical Sciences, Peyton Hall, Ivy Lane, Princeton University, Princeton, NJ 08544, USA

CoI: Todd Tripp, University of Massachusetts
CoI: Timothy Heckman, Johns Hopkins University
CoI: Donald G. York, University of Chicago

Title: Mg II QSO absorption systems: galaxy halos or metal enriched IGM?

Abstract: Mg II QSO absorption lines detected in the spectra of background QSOs have been used to infer that all redshift z>0.2 galaxies have gaseous halos of radius ~eq 60 \h . The actual size of the halo is believed to be proportional to the luminosity of the galaxy. However, these conclusions are now much harder to understand in light of results from hydrodynamical simulations which point to the way in which gas evolves in the universe. These models predict that gas and galaxies merely share the same filamentary structures defined by dark matter. If these models are correct, how are Mg II systems and galaxies really related? We can better understand the distribution of absorbing gas by \it first selecting galaxies close to background QSO sightlines and \it then searching for Mg II absorption at the redshift of the intervening galaxies. This is the antithesis of the experiment carried out a decade ago which sought to find absorbing galaxies \it based on the known existence of a Mg II system. The frequency with which we detect Mg II lines from randomly selected galaxies should enable us to better understand if absorption arises in single galaxy halos, or if the Mg II is merely part of the same IGM that galaxies inhabit, as has been postulated for other types of absorption systems such as \lya or O VI absorbers. With previous NOAO time, we have now identified nearly 30 0.32<z<0.55 galaxies within 60 \h of an QSO sightline. With this proposal, we seek to complete our project by obtaining intermediate resolution spectra of the QSOs themselves to search for Mg II absorption from the intervening galaxy.


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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