NOAO >   Observing Info >   Approved Programs >   2011B-0585

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Proposal Information for 2011B-0585


PI: Eric Monier, The College at Brockport., emonier@brockport.edu
Address: Department of Physics, 350 New Campus Dr., Brockport, NY 14420, USA

CoI: David Turnshek, University of Pittsburgh
CoI: Sandhya Rao, University of Pittsburgh

Title: The Upper Envelope of Cosmic Metallicity near z=1.2 from ZnII-Selected Quasar Absorption Line Systems

Abstract: We are obtaining HST-UV spectroscopy (Cycle 18) to measure HI column densities (N_HI) in eight rare, strong SDSS-ZnII-selected intervening quasar absorption-line systems in the redshift interval z=[1.0,1.4]. UV spectroscopy was already available for two other such systems, bringing our total sample size to ten. Zn is not significantly depleted onto grains and, thus, given our selection method, these systems are representative of the highest absolute columns of neutral- gas-phase metals at moderate redshift. Our HST-UV spectroscopy is showing that they are damped Ly(alpha) (DLA) systems with N_HI \ge 2\times10^20 atoms cm^-2. So far, 5 of 10 systems have been observed with HST, and the Zn metallicities are ~ 0.2, 0.4, 0.8, 0.9, and 2.0 times solar. The HST results will permit us to measure accurate neutral-gas-phase metal abundances (and dust using depletion measures) for any elements that also have accurately-measured, unsaturated neutral-phase metal-line absorption. Here we propose to obtain accurate blue spectroscopy of unsaturated absorption transitions due to SiII, ZnII, CrII, FeII, and MnII to permit this. The higher- quality spectra of these elements will replace the less accurate SDSS spectra which we used to identify the strong-ZnII systems. This work will provide important constraints (i.e., maximum metallicities and relative abundances) on the cosmic chemical evolution and the nature of the most highly evolved systems about 5 Byrs after the Big Bang.


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