NOAO >   Observing Info >   Approved Programs >   2003B-0396

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Proposal Information for 2003B-0396


PI: Kurt Adelberger, Harvard-Smithsonian Center for Astrophysics, kadelber@cfa.harvard.edu
Address: Astrophysics, 60 Garden St MS 51, Cambridge, MA 02138, USA

Title: Measuring the Lifetimes of High-Redshift QSOs

Abstract: This proposal is part of a larger project that aims to measure the lifetimes of QSOs at redshift z~ 2 by observing how far their hydrogen-ionizing radiation has propagated. At this redshift the universe is transparent to ionizing photons and the QSOs' advancing radiation will have altered the ionization balance of the intergalactic medium (IGM) out to a radius of c times the QSO lifetime t_Q. The altered ionization balance will be reflected in decreased Lyman-(alpha) forest absorption in the spectra of any objects that lie behind the QSOs. Thousands of galaxies with R<24.5 will lie behind a typical QSO at z~ 2, and the Lyman-(alpha) forest absorption in their spectra can be used to provide a detailed picture of how the QSO's radiation has penetrated into the IGM. I am requesting 2 nights to obtain deep UGR images of a single MOSAIC field that contains 4 bright QSOs at z~ 2. These images will let me use standard color-selection techniques to find ~ 2000 galaxies at 2.2< z< 2.7 that lie behind the QSOs. Low resolution, low S:N spectra of some of these galaxies will subsequenly be obtained with IMACs on Magellan and will be sufficient to provide a detailed 3D view of the intergalactic volume that has been affected by the QSOs' radiation. This will provide tight constraints on the QSOs' lifetimes and on any possible anisotropy of their emission.


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