NOAO >   Observing Info >   Approved Programs >   2003B-0264

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Proposal Information for 2003B-0264


PI: Michael Rauch, Carnegie Institution of Washington (Headquartes), mr@ociw.edu
Address: Carnegie Observatories, Headquarters, 813 Santa Barbara Street,, Pasadena, CA, 91101-1292, USA

CoI: Francine Marleau, Saint Mary's University
CoI: Martin Haehnelt, University of Cambridge
CoI: James Graham, UC Berkeley (Astronomy)
CoI: Andrew Bunker, University of Cambridge

Title: Fluorescent re-emission of the ionizing UV background from Lyman-limit Systems

Abstract: We propose to detect for the first time the Lyman-alpha fluorescence emission by HI regions at redshift z~2.5-3 which are optically thick to ionizing radiation, using long-slit spectroscopy. The fluorescently emitting Lyman limit systems are expected to be extended with a median diameter of 5arcsec, and about 30 emitters should be detectable with a long (100h) long-slit spectrum with GMOS at a S/N>6x(J[912]/6.0E-22ergs/cm\verb+^+2/s/Hz/sr). Because of the extended nature of the emission this proposal can take advantage of times of poor seeing and the flexibility of the Gemini queue schedule. The universal surface brightness of the fluorescence emission will directly translate into a measurement of the integrated ionizing UV background, to a level as low as J(912)~3.0E- 22ergs/cm\verb+^+2/s/Hz/sr. Such a measurement should settle the longstanding question to what extent galaxies and QSOs contribute to the ionizing background.


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