NOAO >   Observing Info >   Approved Programs >   2009A-0422

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Proposal Information for 2009A-0422


PI: Joseph F. Hennawi, UC Berkeley, joeh@berkeley.edu
Address: Astronomy Department, 601 Campbell Hall, Berkeley, CA 94720-3411, USA

CoI: Michael Gladders, University of Chicago
CoI: Masamune Oguri, Stanford
CoI: Benjamin Koester, University of Chicago
CoI: Matt Bayliss, University of Chicago
CoI: Hakon Dahle, University of Oslo
CoI: Priya Natarajan, Yale

Title: Spectroscopy of Giant Arcs Behind the Strongest Lenses in the Universe

Abstract: We have conducted a deep ((mu)_g \lesssim 24) imaging survey using the WIYN 4-m telescope, the UH 88-inch telescope, and the 2.5m Nordic Optical Telescope (NOT) to search for giant arcs behind the richest clusters identified in the Gpc^3 volume of the SDSS. By imaging nearly 500 massive clusters, this ongoing survey has uncovered some of the most dramatic examples of gravitational lensing ever discovered, similar to `poster-children' like Abell 1689 and CL0024+1654. We propose to use GMOS on Gemini-North and the Blue Channel Spectrograph on the MMT to determine arc redshifts in these new lenses. When combined with our GMOS data from a similar program in 2008A, this proposal will result in a sample of 60 gravitationally lensed galaxies behind ~ 25 clusters. These arc redshifts pinpoint the mass of dark matter interior to the Einstein radius in the cluster core (R < 200\hkpc; comoving). The larger scale (R ~ 1-5\hMpc) weak lensing shear has been measured for more than half of our targets from deep imaging at NOT, WIYN, Subaru, and using archival data from HST. GMOS arc redshifts combined with weak and strong lensing will allow us to measure the density profile of dark matter halos on scales 200\hkpc < R < 5\hMpc for the statistical sample of lensing clusters, providing a powerful test of the (Lambda)CDM paradigm.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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