Constraining cosmology using galaxy position angle-only cosmic shear
  We investigate cosmological parameter inference from realistic simulated weak
lensing image data using only galaxy position angles, as opposed to
full-ellipticity information. We demonstrate that input shear fields can be
accurately reconstructed using only the statistics of source galaxy position
angles and that, from these shear fields, we can successfully recover power
spectra and infer the input cosmology. This paper builds on previous work on
angle-only weak lensing estimation by extending the method to deal with
variable and anisotropic PSF convolution and variable shear fields. Previous
work employed a weighting scheme to downweight the contribution to shear
estimates from sources aligned with the PSF. This work removes the need to
downweight sources by convolving them with an image of the PSF rotated by
$90^{\circ}$. We show thats this successfully undoes the rotation caused by PSF
convolution, assuming we have reliable images of the PSF. We find that we can
accurately recover the input shear signal from a simulated Stage III-like weak
lensing data set using only the position angles to within an overall scale
factor, and that the scale factor can be determined using a cosmology
independent simulation with noise, galaxy, and PSF properties that match the
observed data set. We then demonstrate that we can constrain cosmological
parameters using angle-only shear estimates with a constraining power
comparable to using current state-of-the-art shape measurement techniques that
provide full-ellipticity information.
