Constraining the epoch of reionization with the variance statistic: Simulations of the LOFAR case

Ajinkya H. Patil, Saleem Zaroubi, Emma Chapman, Vibor Jelić, Geraint Harker, Filipe B. Abdalla, Khan M.B. Asad, Gianni Bernardi, Michiel A. Brentjens, A. G. de Bruyn, Sander Bus, Benedetta Ciardi, Soobash Daiboo, Elizabeth R. Fernandez, Abhik Ghosh, Hannes Jensen, Sanaz Kazemi, Léon V.E. Koopmans, Panagiotis Labropoulos, Maaijke MeviusOscar Martinez, Garrelt Mellema, Andre R. Offringa, Vishhambhar N. Pandey, Joop Schaye, Rajat M. Thomas, Harish K. Vedantham, Vamsikrishna Veligatla, Stefan J. Wijnholds, Sarod Yatawatta

Research output: Contribution to journalArticlepeer-review


Several experiments are underway to detect the cosmic-redshifted 21-cm signal from neutral hydrogen from the Epoch of Reionization (EoR). Due to their very low signal-to-noise 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 Low-Frequency 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 (zr) and duration (Δz) of reionization can be constrained assuming a parametrization. We use an EoR simulation of zr = 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 zr = 7.72+0.37 -0.18 and Δz = 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 cross-variance of the signal by cross-correlating consecutive redshift bins.

Original languageEnglish
Pages (from-to)1113-1124
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
StatePublished - Apr 2014
Externally publishedYes


  • Dark ages, reionization, first stars
  • Methods: statistical
  • Techniques: interferometric


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