NOAO >   Observing Info >   Approved Programs >   2003B-0108

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Proposal Information for 2003B-0108


PI: Sangeeta Malhotra, Space Telescope Science Institute, san@stsci.edu
Address: 3700 San Martin Drive, Baltimore, MD 21218, USA

CoI: James Rhoads, Space Telescope Science Institute

Title: Lyman Alpha Galaxies During and After Reionization

Abstract: The formation of galaxies and the reionization of the intergalactic medium are major milestones in cosmic history that are only now becoming accessible to observation. \lya emission from star-forming galaxies offers a powerful probe of both. \lya line emission is an efficient tool for identifying young galaxies at high redshift, being strong in galaxies with young stars and little or no dust. Faint \lya emitters also provide a robust test of reionization, as in they should not be visible in a neutral IGM. Even strong sources should have the \lya\ line attenuated by the damping wings of HI. We propose narrow-band imaging to find \lya emitters at redshifts z=5.7 and 6.6, spanning the end of reionization at z \appx 6. By comparing the numbers and equivalent widths of the \lya line emitters, we will (\bf A) determine the luminosity function of \lya emitters, which are one likely source of ionizing photons; (\bf B) characterize galaxy formation and evolution at z=5.7 and 6.6 by determining the halo masses, occupation numbers, and duty cycle of \lya emitters; (\bf C) characterize star-formation at z=5.7 and 6.6; (\bf D) constrain the epoch of reionization. The Large Area Lyman Alpha survey at NOAO has succesfully found large samples of \lya galaxies at z=4.5 and 5.7 with typical spectroscopic followups success of \appx 75-80%. The \lya equivalent widths demonstrate that these source are likely younger than 10 Myrs, with low metallicity and a larger fraction of massive stars. With the current proposal we expect to find \appx 40 lya\ emitters at z=5.7 and \appx 5 at z=6.6. These observations would give us larger samples at these redshifts as well more robust statistics by sampling more than one patch of sky.


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