Reionization by hard photons. I. X-rays from the first star clusters

被引:161
作者
Oh, SP [1 ]
机构
[1] Princeton Univ Observ, Princeton, NJ 08544 USA
关键词
cosmology : theory; galaxies : formation; intergalactic medium;
D O I
10.1086/320957
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Observations of the Ly alpha forest at z similar to3 reveal an average metallicity Z similar to 10(-2) Z(circle dot). The high-redshift supernovae that polluted the intergalactic medium also accelerated relativistic electrons. Since the energy density of the cosmic microwave background is proportional to (1+z)(4), at high redshift these electrons cool via inverse Compton scattering. Thus, the first star clusters emit X-rays. Unlike stellar UV ionizing photons, these X-rays can escape easily from their host galaxies. This has a number of important physical consequences: 1. Owing to their large mean free path, these X-rays can quickly establish a universal ionizing background and partially reionize the universe in a gradual, homogeneous fashion. If X-rays formed the dominant ionizing background, the universe would have more closely resembled a single-phase medium rather than a two-phase medium. 2. X-rays can reheat the universe to higher temperatures than possible with UV radiation. 3. X-rays counter the tendency of UV radiation to photodissociate H-2,an important coolant in the early universe, by promoting gas-phase H-2 formation. The X-ray production efficiency is calibrated to local observations of starburst galaxies, which imply that similar to 10% of the supernova energy is converted to X-rays. While direct detection of sources in X-ray emission is difficult, the presence of relativistic electrons at high redshift and thus a minimal level of X-ray emission may be inferred by synchrotron emission observations with the Square Kilometer Array. These sources may constitute a significant fraction of the unresolved hard X-ray background and can account for both the shape and amplitude of the gamma-ray background. This paper discusses the existence and observability of high-redshift X-ray sources, while a companion paper models the detailed reionization physics and chemistry.
引用
收藏
页码:499 / 512
页数:14
相关论文
共 127 条
[1]  
ABEL T, 1999, EVOLUTION LARGE SCAL, P363
[2]  
Aghanim N, 1996, ASTRON ASTROPHYS, V311, P1
[3]   GALAXIES AND GAMMA-RAY ASTRONOMY [J].
BIGNAMI, GF ;
FICHTEL, CE ;
HARTMAN, RC ;
THOMPSON, DJ .
ASTROPHYSICAL JOURNAL, 1979, 232 (03) :649-658
[4]   Dust-obscured star formation and AGN fuelling in hierarchical models of galaxy evolution [J].
Blain, AW ;
Jameson, A ;
Smail, I ;
Longair, MS ;
Kneib, JP ;
Ivison, RJ .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1999, 309 (03) :715-730
[5]  
BLAIN AW, 2000, ASP C SER, V193, P425
[6]   PARTICLE-ACCELERATION AT ASTROPHYSICAL SHOCKS - A THEORY OF COSMIC-RAY ORIGIN [J].
BLANDFORD, R ;
EICHLER, D .
PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, 1987, 154 (01) :1-75
[7]  
BLANDHAWTHORN J, 1999, APJ, V510, P33
[8]   THE COSMIC X-RAY-BACKGROUND [J].
BOLDT, E .
PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, 1987, 146 (04) :215-257
[9]   THE CONTRIBUTION OF YOUNG GALAXIES TO THE X-RAY-BACKGROUND [J].
BOOKBINDER, J ;
COWIE, LL ;
KROLIK, JH ;
OSTRIKER, JP ;
REES, M .
ASTROPHYSICAL JOURNAL, 1980, 237 (03) :647-654
[10]   HIGH-RESOLUTION X-RAY-IMAGING OF THE STARBURST GALAXY M82 [J].
BREGMAN, JN ;
SCHULMAN, E ;
TOMISAKA, K .
ASTROPHYSICAL JOURNAL, 1995, 439 (01) :155-162