Constraining the epoch of reionization with the variance statistic: simulations of the LOFAR case
Abstract
Several experiments are underway to detect the cosmicredshifted 21cm signal from neutral hydrogen from the Epoch of Reionization (EoR). Due to their very low signaltonoise ratio, these observations aim for a statistical detection of the signal by measuring its power spectrum. We investigate the extraction of the variance of the signal as a first step towards detecting and constraining the global history of the EoR. Signal variance is the integral of the signal's power spectrum, and it is expected to be measured with a high significance. We demonstrate this through results from a simulation and parameter estimation pipeline developed for the LowFrequency Array (LOFAR)EoR experiment. We show that LOFAR should be able to detect the EoR in 600 h of integration using the variance statistic. Additionally, the redshift (z_{r}) and duration (Δz) of reionization can be constrained assuming a parametrization. We use an EoR simulation of z_{r} = 7.68 and Δz = 0.43 to test the pipeline. We are able to detect the simulated signal with a significance of four standard deviations and extract the EoR parameters as z_r = 7.72^{+0.37}_{0.18} and Δ z = 0.53^{+0.12}_{0.23} in 600 h, assuming that systematic errors can be adequately controlled. We further show that the significance of detection and constraints on EoR parameters can be improved by measuring the crossvariance of the signal by crosscorrelating consecutive redshift bins.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 September 2014
 DOI:
 10.1093/mnras/stu1178
 arXiv:
 arXiv:1401.4172
 Bibcode:
 2014MNRAS.443.1113P
 Keywords:

 methods: statistical;
 techniques: interferometric;
 dark ages;
 reionization;
 first stars;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 13 pages, 14 figures, Accepted for publication in MNRAS