Open AccessMorphology of the secondary cosmic microwave background anisotropies: the key to ‘smouldering’ reionization
Author(s) -
Gnedin Nickolay Y.,
Shandarin Sergei F.
Publication year - 2002
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2002.06035.x
Subject(s) - reionization , physics , cosmic microwave background , astrophysics , redshift , astronomy , excursion , universe , dark ages , hydrogen line , cosmic background radiation , anisotropy , galaxy , optics , law , political science
We show how the morphological analysis of the maps of the secondary cosmic microwave background anisotropies can detect an extended period of ‘smouldering’ reionization, during which the Universe remains partially ionized. Neither radio observations of the redshifted 21‐cm line nor infrared observations of the redshifted Lyman‐alpha forest will be able to detect such a period. The most sensitive parameters to this kind of non‐Gaussianity are the number of regions in the excursion set, N cl , the perimeter of the excursion set, P g , and the genus (i.e. ‘1 – number of holes’) of the largest (by area) region. For example, if the Universe reionized fully at z = 6 , but maintained about 1/3 mean ionized fraction as z = 20 , then a 2 ‐arcmin map with 500 2 pixel resolution and a signal‐to‐noise ratio S/N = 1/2 allows us to detect the non‐Gaussianity due to reionization with better than 99 per cent confidence level.