Measuring Dark Matter Substructure with Galaxy-Galaxy Flexion Statistics
  It is of great interest to measure the properties of substructures in dark
matter halos at galactic and cluster scales. Here we suggest a method to
constrain substructure properties using the variance of weak gravitational
flexion in a galaxy-galaxy lensing context. We show the effectiveness of
flexion variance in measuring substructures in N-body simulations of dark
matter halos, and present the expected galaxy-galaxy lensing signals. We show
the insensitivity of the method to the overall galaxy halo mass, and predict
the method's signal-to-noise for a space-based all-sky survey, showing that the
presence of substructure down to 10^9 M_\odot halos can be reliably detected.
