Quantifying densityionization correlations with the 21cm power spectrum
Abstract
The epoch of reionization (EoR)  when neutral hydrogen in the intergalactic medium was systematically ionized  is a period in our Universe's history that is currently poorly understood. However, a key prediction of most models is a correlation between the density and ionization field during the EoR. This has consequences for the 21cm power spectrum. Here, we propose a parametrization for the densityionization correlation and study the dependence of the 21cm power spectrum on this parametrization. We use this formalism to forecast the ability of current and future observations to constrain these correlations. We find that upper limits on the dimensionless power spectrum at redshifts 7.5 < z < 8.5 using k bins between $0.1 \lt k \lt 0.75\, \textrm {Mpc}^{1}$ with error bars at the level of ${\sim\! }20\, \textrm {mK}^2$ about our fiducial model would rule out uncorrelated reionization at $99{{\ \rm per\ cent}}$ credibility. Beyond upper limits, we find that at its full sensitivity, the Hydrogen Epoch of Reionization Array (HERA) will be able to place strong constraints on the sign and magnitude of densityionization correlations.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 October 2020
 DOI:
 10.1093/mnras/staa2118
 arXiv:
 arXiv:2005.11326
 Bibcode:
 2020MNRAS.498..373P
 Keywords:

 methods: observational;
 methods: statistical;
 dark ages;
 reionization;
 first stars;
 largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 12 pages, 10 figures. Replaced to match accepted MNRAS version