Friday, April 19, 2013

1304.4992 (Takashi Hamana et al.)

Toward understanding the anisotropic point spread function of Suprime-Cam and its impact on cosmic shear measurement    [PDF]

Takashi Hamana, Satoshi Miyazaki, Yuki Okura, Tomohiro Okamura, Toshifumi Futamase
We examine the anisotropic point spread function (PSF) of Suprime-Cam data utilizing the dense star field data. We decompose the PSF ellipticities into three components, the optical aberration, atmospheric turbulence and chip-misalignment in an empirical manner, and evaluate the amplitude of each component. We find that, for long-exposure data, the optical aberration has the largest contribution to the PSF ellipticities, which can be modeled well by a simple analytic function based on the lowest-order aberration theory. Statistical properties of PSF ellipticities originated from the atmospheric turbulence are investigated by using the numerical simulation, and it is found that simulation results are in a reasonable agreement with the observed data. It is also found that the optical PSF can be well corrected by the standard correction method with polynomial fitting function. However, for the atmospheric PSF, its correction suffers from the common limitation arisen from sparse sampling of PSFs due to a limited number of stars. We also examine effects of the residual PSF anisotropies on Suprime-Cam cosmic shear data. We find that the shape and amplitude of B-mode shear variance are broadly consistent with those of the residual PSF ellipticities measured from the dense star field data. This indicates that most of the sources of residual systematic are understood, which is an important step for cosmic shear statistics to be a practical tool of the precision cosmology.
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