Constraining Extended Reionization Models Through Arcminute-Scale CMB
  Measurements
  The measurement of the optical depth to free electrons, tau_r, in the cosmic
microwave background (CMB) provides an important constraint on reionization,
but is degenerate to more complex reionization models. Small angular-scale CMB
measurements of the kinetic Sunyaev-Zeldovich (kSZ) and Ostriker-Vishniac (OV)
effects have the potential to break this degeneracy. We calculate the OV signal
for various extended reionization histories described by a simple analytic
form. These models are parametrized by dz, the duration of the reionization
event. For reionization histories with identical values of tau_r, the OV
amplitude at l = 3000 (C_3000) differs by ~20 % between the models with dz =
0.1 and dz = 3.0. We demonstrate that the removal of the z < 6 component of the
OV signal will significantly enhance the ability to differentiate between
reionization histories, with C_3000 varying by a factor of ~2 between the
models with dz = 0.1 and dz = 3.0. If the low-redshift OV and related kSZ
signal can be adequately subtracted, this would provide an important
observational constraint on extended reionization models.
