Constraining Extended Reionization Models through Arcminute-scale Cmb Measurements

The measurement of the optical depth to free electrons, τr, 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 ∆z , the duration of the reionization event. For reionization histories with identical values of τr , the OV amplitude at l = 3000 (C3000) differs by ≈ 20% between the models with ∆z = 0.1 and ∆z = 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 C3000 varying by a factor of ∼ 2 between the models with ∆z = 0.1 and ∆z = 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. Subject headings: cosmology: theory — cosmology: observations — cosmic microwave background — large-scale structure of universe — radiation mechanisms: non-thermal — scattering