How is the Reionization Epoch Defined?

Abstract

We study the effect of a prolonged epoch of reionization on the angular power spectrum of the Cosmic Microwave Background. Typically reionization studies assume a sudden phase transition, with the intergalactic gas moving from a fully neutral to a fully ionized state at a fixed redshift. Such models are at odds, however, with detailed investigations of reionization, which favor a more extended transition. We have modified the code CMBFAST to allow the treatment of more realistic reionization histories and applied it to data obtained from numerical simulations of reionization. We show that the prompt reionization assumed by CMBFAST in its original form heavily contaminates any constraint derived on the reionization redshift. We find, however, that prompt reionization models give a reasonable estimate of the epoch at which the mean cosmic ionization fraction was ~50%, and provide a very good measure of the overall Thomson optical depth. The overall differences in the temperature (polarization) angular power spectra between prompt and extended models with equal optical depths are less than 1% (10%).

5 pages, 3 figures; accepted on MNRAS

References in corpus (1)

• Why do starless cores appear more flattened than protostellar cores?

Cited by in corpus (18)

• The First Cosmic Structures and their Effects
• Early Reionization by the First Galaxies
• Probing the Reionization History of the Universe using the Cosmic Microwave Background Polarization
• Model-Independent Reionization Observables in the CMB
• The Reionization History at High Redshifts II: Estimating the Optical Depth to Thomson Scattering from CMB Polarization
• Measuring $\alpha$ in the Early Universe: CMB Polarization, Reionization and the Fisher Matrix Analysis
• The First Generation of Star-Forming Haloes
• Constraining the helium abundance with CMB
• Large-Scale Simulations of Reionization
• Illuminating the dark ages: Cosmic backgrounds from accretion onto primordial black hole dark matter
• Relativistic Ionization Fronts
• Reionization History from Coupled CMB/21cm Line Data
• Studying cosmic reionization with observations of the global 21-cm signal
• 1.4 GHz polarimetric observations of the two fields imaged by the DASI experiment
• Cosmic Microwave Background Polarization and reionization: constraining models with a double reionization
• Constraining the reionization history with large angle CMB polarization
• Cosmic opacity to CMB photons and polarization measurements
• Nature of Dark Energy and Polarization Measurements