Intrinsic and extrinsic correlations of galaxy shapes and sizes in weak
  lensing data
  The subject of this paper is to build a physical model describing shape and
size correlations of galaxies due to weak gravitational lensing and due to
direct tidal interaction of elliptical galaxies with gravitational fields
sourced by the cosmic large-scale structure. Setting up a linear intrinsic
alignment model for elliptical galaxies which parameterises the reaction of the
galaxy to an external tidal shear field is controlled by the velocity
dispersion, we predict intrinsic correlations and cross-correlations with weak
lensing for both shapes and sizes, juxtaposing both types of spectra with
lensing. We quantify the observability of the intrinsic shape and size
correlations and estimate with the Fisher-formalism how well the alignment
parameter can be determined from the Euclid weak lensing survey. Specifically,
we find a contamination of the weak lensing convergence spectra with an
intrinsic size correlation amounting to up to 10% over a wide multipole range
$\ell=100\ldots300$, with a corresponding cross-correlation exhibiting a sign
change, similar to the cross-correlation between weak lensing shear and
intrinsic shapes. A determination of the alignment parameter yields a precision
of a few percent forecasted for Euclid, and we show that all shape and many
size correlations should be measurable with Euclid.
