AAS 207th Meeting, 8-12 January 2006
Session 26 LSST
Poster, Monday, 9:20am-7:00pm, January 9, 2006, Exhibit Hall

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[26.12] Observational Validation of LSST Image Quality Requirements

S. Asztalos (LLNL), D. Burke (SLAC), C. F. Claver (NOAO), S. Heathcote (SOAR, NOAO), L. Rosenberg (LLNL), A. Becker (U. Washington), M. Britton, B. Ellerbroek (Cal Tech), K. Gilmore (SLAC), M.-C. Hainaut-Rouelle (Gemini), G. Jernigan (Berkeley SSL and SLAC), S. M. Kahn (SLAC), V. Krabbendam (NOAO), V. Margoniner (UC Davis), D. Monet (USNO), J. R. Peterson (SLAC), P. Pinto (U. Arizona), P. Puxley, P. Puxley (Gemini), A. Rasmussen (SLAC), J. Sebag (NOAO), L. Simms (SLAC), A. Tokovinin (NOAO), J.A. Tyson, D. Wittman (UC Davis)

Cosmic shear provides a completely independent method for estimating \Omega\rm m, the amount of matter density in the universe relative to the critical density. In a manner similar to that employed in CMB analyses, a power spectrum is constructed from two-point correlations in shear space. The shear spectrum formed in this way can be directly compared with predictions from cosmological models.

The LSST statistical errors on the shear power spectrum will be very small, so that keeping systematic errors below this level will be a challenge. Here we investigate one systematic: the atmosphere, which will inject spurious power on small scales. An investigation using the 8-m Subaru telescope with LSST-like exposure times shows that the shear residuals from the atmosphere are comfortably less than the expected statistical errors.

Discretionary time on the Gemini telescope in conjunction with site MASS-DIMM data was obtained to further explore the effects of seeing on object ellipticity. We find that ellipticity correlations which extend out to 1' under good seeing conditions vanish when the seeing approaches 1''. Scales larger than 1' are most important for cosmology, and at these scales the correlations are small in all seeing conditions. Furthermore, correlations can be well corrected using a realistic density of PSF stars. We have also analyzed the distribution of correlation lengths for instances of good and bad seeing. Finally, we present results on wind direction and ellipticity correlation length.

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