NOAO >   Observing Info >   Approved Programs >   2011B-0538

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Proposal Information for 2011B-0538


PI: S. Mark Ammons, Lawrence Livermore National Laboratory, ammons@as.arizona.edu
Address: Physics Department, 7000 East Ave., Livermore, CA 94550, USA

CoI: Kenneth C. Wong, University of Arizona
CoI: Ann I. Zabludoff, University of Arizona
CoI: Charles R. Keeton, Rutgers University

Title: Finding the Most Powerful Gravitational Lens Telescopes with MMT Hectospec

Abstract: Detecting the earliest galaxies at z \gtrsim 7 is a major challenge. Past studies have required a large investment of \emphHST time and have only detected a handful of candidates. While gravitational lensing by a foreground galaxy cluster can make a given source easier to detect, it reduces the overall volume surveyed. Hence, there is much discussion of the trade-offs between different methodologies. To resolve this debate, we have developed a new theoretical framework that quantifies the lensing effects of different line-of-sight mass distributions on the detectability of z \gtrsim 7 sources. We find configurations of multiple superposed structures that could produce a ~ 10 \times increase in the number of detected z \gtrsim 7 sources compared to blank field surveys. We have identified the 40 lines-of-sight in the Sloan Digital Sky Survey with the highest integrated luminosity densities. These beams are likely to be the most powerful gravitational lens telescopes in the sky. For three of the densest beams, we propose to use MMT/Hectospec to obtain redshifts for ~200 centralized galaxies and ~1000 total galaxies per field to determine how the mass is distributed in redshift space. This detailed mass model will constrain the regions of ideal magnification which are most likely to result in the detection of z > 7 galaxies. This program follows a successful pilot spectroscopic program with MMT/Hectospec and is complemented by an imaging proposal to obtain positions and colors for giant arcs in these fields.


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