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Light cone anisotropy in the 21 cm signal from the epoch of reionization

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dc.contributor.author Zawada, Karolina
dc.contributor.author Semelin, Benoît
dc.contributor.author Vonlanthen, Patrick
dc.contributor.author Baek, Sunghye
dc.contributor.author Revaz, Yves
dc.date.accessioned 2014-02-13T09:52:20Z
dc.date.available 2014-02-13T09:52:20Z
dc.date.issued 2014-01
dc.identifier.citation Monthly Notices of the Royal Astronomical Society , 2014
dc.identifier.issn 1365-2966
dc.identifier.other doi:10.1093/mnras/stu035
dc.identifier.uri http://repozytorium.umk.pl/handle/item/1700
dc.description doi:10.1093/mnras/stu035 arXiv:1401.1807
dc.description.abstract Using a suite of detailed numerical simulations we estimate the level of anisotropy generated by the time evolution along the light cone of the 21 cm signal from the epoch of reionization. Our simulations include the physics necessary to model the signal during both the late emission regime and the early absorption regime, namely X-ray and Lyman-band 3D radiative transfer in addition to the usual dynamics and ionizing UV transfer. The signal is analysed using correlation functions perpendicular and parallel to the line of sight. We reproduce general findings from previous theoretical studies: the overall amplitude of the correlations and the fact that the light cone anisotropy is visible only on large scales (100 comoving Mpc). However, the detailed behaviour is different. We find that, at three different epochs, the amplitude of the correlations along and perpendicular to the line of sight differ from each other, indicating anisotropy. We show that these three epochs are associated with three events of the global reionization history: the overlap of ionized bubbles, the onset of mild heating by X-rays in regions around the sources, and the onset of efficient Lyman-α coupling in regions around the sources. We find that a 20×20 deg^2 survey area may be necessary to mitigate sample variance when we use the directional correlation functions. On a 100 Mpc (comoving) scale, we show that the light cone anisotropy dominates over the anisotropy generated by peculiar velocity gradients computed in the linear regime. By modelling instrumental noise and limited resolution, we find that the anisotropy should be easily detectable by the Square Kilometre Array, assuming perfect foreground removal, the limiting factor being a large enough survey size. In the case of the Low-Frequency Array for radio astronomy, it is likely that only one anisotropy episode (ionized bubble overlap) will fall in the observing frequency range. This episode will be detectable only if sample variance is much reduced (i.e. a larger than 20 × 20 deg^2 survey, which is not presently planned).
dc.language.iso eng
dc.publisher Oxford University Press
dc.rights info:eu-repo/semantics/openAccess
dc.subject numerical simulation
dc.subject reionization
dc.subject early Universe
dc.subject large scale structure
dc.title Light cone anisotropy in the 21 cm signal from the epoch of reionization
dc.type info:eu-repo/semantics/article


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