NAOC Open IR  > 星系宇宙学研究部
The reionization history in the lognormal model
Liu, JR; Fang, LZ; Feng, LL; Bi, HG
AbstractWe study the evolution of baryonic gas before reionization in the lognormal (LN) model of cosmic clustering. We show that the thermal history of the universe around reionization can roughly be divided into three epochs: (1) a cold dark age z > z(r), in which the baryon gas is neutral and opaque to Lyalpha photons; (2) a hot dark age z(r) > z > z(GP), in which a predominant part of the baryon gas is ionized and hot but is still opaque to Lyalpha photons; and (3) a bright age z < z(GP), in which the universe is ionized enough to be transparent to Lyα photons. In the flat cold dark matter cosmological models given by WMAP and COBE, the difference of the two redshifts z(r) - z(GP) is found to be as large as &SIM;10, with z(r) &SIM; 17 and z(GP) &SIM; 7. This reionization history naturally yields a high optical depth of the CMB τ(e) &SIME; 0.12-0.19, which is observed in the TE polarization in the WMAP data, and a low redshift z(GP) for the appearance of the Lyα Gunn-Peterson trough, z(GP) &SIME; 6-8, in QSO absorption spectra. The universe stays so long in an ionized, yet Lyα opaque, stage because the first photoionization heats the inter-galactic gas effectively and balances the gravitational clustering for a long period of time. Therefore, a high τ(e) and low z(GP) is a result of all the considered models. Besides the cosmological parameters, the only free parameter we used in the calculation is N-ion, the mean number of ionization photons produced by each baryon in collapsed objects. We take it to be 40-80 in the calculations.
KeywordCosmology : Theory Early Universe Large-scale Structure Of Universe
Indexed BySCI
WOS IDWOS:000220801900002
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Document Type期刊论文
Affiliation1.Univ Sci & Technol China, Ctr Astrophys, Anhua 230026, Peoples R China
2.Univ Arizona, Dept Phys, Tucson, AZ 85721 USA
3.Chinese Acad Sci, Natl Astron Observ, Beijing 100012, Peoples R China
Recommended Citation
GB/T 7714
Liu, JR,Fang, LZ,Feng, LL,et al. The reionization history in the lognormal model[J]. ASTROPHYSICAL JOURNAL,2004,605(2):591-598.
APA Liu, JR,Fang, LZ,Feng, LL,&Bi, HG.(2004).The reionization history in the lognormal model.ASTROPHYSICAL JOURNAL,605(2),591-598.
MLA Liu, JR,et al."The reionization history in the lognormal model".ASTROPHYSICAL JOURNAL 605.2(2004):591-598.
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