Stacking for Cosmic Magnetism with SKA Surveys
  Stacking polarized radio emission in SKA surveys provides statistical
information on large samples that is not accessible otherwise due to
limitations in sensitivity, source statistics in small fields, and averaging
over frequency (including Faraday synthesis). Polarization is a special case
because one obvious source of stacking targets is the Stokes I source catalog,
possibly in combination with external catalogs, for example an SKA HI survey or
a non-radio survey. We point out the significance of stacking sub-samples
selected by additional observable parameters to investigate relations that
reveal more about the physics of the source. Applications of stacking
polarization include, but are not limited to, obtaining in a statistical sense
polarization information to the detection limit in total intensity,
depolarization as a function of cosmic time at consistent source-frame
wavelengths, magnetic field properties in objects with a low radio luminosity
such as dwarf and low-surface-brightness galaxies, and investigating potential
correlations of observable parameters with the average magnetic field direction
in a sample. We also point out the potential use of stacking in validating the
polarization calibration of a survey. While stacking is flexible in terms of
survey definition, we discuss optimal survey parameters for the science
experiments presented, as well as computing and archiving requirements.
