Morphological properties of blazar-induced gamma-ray haloes
  At TeV energies and above gamma rays can induce electromagnetic cascades,
whose charged component is sensitive to intervening intergalactic magnetic
fields (IGMFs). When interpreting gamma-ray measurements in the energy range
between a few GeV and hundreds of TeV, one has to carefully account for effects
due to IGMFs, which depend on their strength and power spectrum. Therefore,
gamma-ray-induced electromagnetic cascades can be used as probes of cosmic
magnetism, since their arrival distribution as well as spectral and temporal
properties can provide unique information about IGMFs, whose origin and
properties are currently poorly understood. In this contribution we present an
efficient three-dimensional Monte Carlo code for simulations of gamma-ray
propagation. We focus on the effects of different configurations of IGMFs, in
particular magnetic helicity and the power spectrum of stochastic fields, on
the morphology of the arrival directions of gamma rays, and discuss the
prospects for detecting pair haloes around distant blazars.
