Toward understanding the anisotropic point spread function of
  Suprime-Cam and its impact on cosmic shear measurement
  We examined the anisotropic point spread function (PSF) of Suprime-Cam data
utilizing dense star field data. We decomposed the PSF ellipticities into three
components, the optical aberration, atmospheric turbulence, and
chip-misalignment in an empirical manner, and evaluated the amplitude of each
component. We found that, for long-exposure data, the optical aberration has
the largest contribution to the PSF ellipticities, which could be modeled well
by a simple analytic function based on the lowest-order aberration theory. The
statistical properties of PSF ellipticities resulting from the atmospheric
turbulence were investigated by using the numerical simulations. The 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 a polynomial fitting function. However, for the atmospheric PSF, its
correction is affected by the common limitation caused by sparse sampling of
PSFs due to a limited number of stars. We also examined the effects of the
residual PSF anisotropies on Suprime-Cam cosmic shear data. We found that the
shape and amplitude of the 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.
