Title:	Hydrogen 2p–2s Transition: Signals from the Epochs of Recombination and Reionization
Authors:	Sethi, S.K. Subrahmanyan, Ravi Roshi, Anish D.
Keywords:	Cosmic Microwave Background Line: Formation Radiative Transfer Radio Lines: General
Issue Date:	Jul-2007
Publisher:	The University of Chicago Press for the American Astronomical Society
Citation:	The Astrophysical Journal, 2007, Vol.664, p1-7.
Abstract:	We propose a method to study the epoch of reionization based on the possible observation of 2p-2s fine-structure lines from the neutral hydrogen outside the cosmological H II regions enveloping QSOs and other ionizing sources in the reionization era. We show that for parameters typical of luminous sources observed at z~=6.3, the strength of this signal, which is proportional to the H I fraction, has a brightness temperature ~=20 μK for a fully neutral medium. The fine-structure line from this redshift is observable at ν~=1 GHz, and we discuss prospects for the detection with several operational and future radio telescopes. We also compute the characteristics of this signal from the epoch of recombination; the peak brightness is expected to be ~=100 μK, and this signal appears in the frequency range 5-10 MHz. The signal from the recombination era is nearly impossible to detect owing to the extreme brightness of the Galactic emission at these frequencies.
Description:	Restricted Access. Articles older than 2 years are open to all at the journal site (alternative location)
URI:	http://hdl.handle.net/2289/3334
ISSN:	E-ISSN: 1538-4357 P-ISSN: 0004-637X
Alternative Location:	http://adsabs.harvard.edu/cgi-bin/bib_query?2007ApJ...664....1S http://arxiv.org/abs/0704.1226 http://dx.doi.org/10.1086/518650
Copyright:	2007 The American Astronomical Society
Appears in Collections:	Research Papers (A&A)

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