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Cosmic reionization and the 21 cm signal: comparison between an analytical model and a simula

Santos, Mário G. and Amblard, Alexandre and Pritchard, Jonathan and Trac, Hy and Cen, Renyue and Cooray, Asantha (2008) Cosmic reionization and the 21 cm signal: comparison between an analytical model and a simula. Astrophysical Journal, 689 (1). pp. 1-16. ISSN 0004-637X.

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We measure several properties of the reionization process and the corresponding low-frequency 21 cm signal associated with the neutral hydrogen distribution, using a large volume, high-resolution simulation of cosmic reionization. The brightness temperature of the 21 cm signal is derived by postprocessing this numerical simulation with a semianalytical prescription. Our study extends to high redshifts (z ~ 25) where, in addition to collisional coupling, our postprocessed simulations take into account the inhomogeneities in the heating of the neutral gas by X-rays and the effect of an inhomogeneous Ly α radiation field. Unlike the well-studied case in which spin temperature is assumed to be significantly greater than the temperature of the cosmic microwave background due to uniform heating of the gas by X-rays, spatial fluctuations in both the Ly α radiation field and X-ray intensity affect predictions related to the brightness temperature at z > 10, during the early stages of reionization and gas heating. The statistics of the 21 cm signal from our simulation are then compared to existing analytical models in the literature, and we find that these analytical models provide a reasonably accurate description of the 21 cm power spectrum at z < 10. Such an agreement is useful, since analytical models are better suited to quickly explore the full astrophysical and cosmological parameter space relevant for future 21 cm surveys. We find, nevertheless, nonnegligible differences that can be attributed to differences in the inhomogeneous X-ray heating and Lyα coupling at z > 10, and, with upcoming interferometric data, these differences in return can provide a way to better understand the astrophysical processes during reionization.

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Additional Information:© 2008 The American Astronomical Society. Received 2007 August 21; accepted 2008 July 20. This work was partially supported by FCT-Portugal under grant PTDC/FIS/66825/2006 and was supported at the University of California, Irvine, by NSF CAREER AST 06-45427 and by the National Aeronautics and Space Administration (NASA) through grant number 11242 from the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555. This research is also supported in part by grants AST 04-07176 and NNG06GI09G. A. A. is supported in part by a McCue Fellowship. H. T. is supported in part by NASA grant LTSA-03-000-0090. M. G. S. was partially supported by FCT Portugal under grant BPD/17068/2004/Y6F6. J. P. is supported by NASA through Hubble Fellowship grant HST-HF-01211.01-A, awarded by STScI.
Funding AgencyGrant Number
Fundação para a Ciência e a Tecnologia (FCT) PortugalPTDC/FIS/66825/2006
NASAAST 04-07176
Fundação para a Ciência e a Tecnologia (FCT) PortugalBPD/17068/2004/Y6F6
Hubble FellowshipHST-HF-01211.01-A
Subject Keywords:cosmology: theory; diffuse radiation; large-scale structure of universe
Record Number:CaltechAUTHORS:20090527-111453216
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14317
Deposited By: Tony Diaz
Deposited On:27 May 2009 23:02
Last Modified:27 Mar 2014 05:40

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