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arXiv 1607.02664astro-ph.GAastro-ph.CO
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Pop III余迹的高红移X射线背景:文艺复兴模拟中Pop III恒星形成率的结果

X-ray Background at High Redshifts from Pop III Remnants: Results from Pop III star formation rates in the Renaissance Simulations

Hao Xu, Kyungjin Ahn, Michael L Norman, John H Wise, Brian W O'Shea

摘要:

由于X射线具有较长的平均自由程,因此X射线在大尺度上的加热和电离过程将对星系际介质(IGM)的性质产生重大影响。在高红移时,来自星族(Pop)III双星的X射线可能对宇宙再电离和莱曼α森林有重要影响。作为我们之前关于Pop III双星X射线的工作(Xu et al. 2014)的延续,我们使用来自Renaissance Simulations的Pop III分布和演化,这是第一个星系形成的一套自洽宇宙辐射流体力学模拟,以计算红移范围20 > z > 7.6的X射线光度密度和背景。由于我们发现Pop III恒星的形成以一个低的、几乎恒定的速率持续到再电离的结束,与其他可能的X射线源相比,X射线正在以显著的速率持续产生,如活动星系核和正常的X射线双星在同一时期。我们估计,Pop III双星产生约6电子伏特的能量在X射线每氢原子。计算了不同单色光子能量下的X射线本底。KeV的X射线会发生红移并积累,从而产生一个强的X射线背景光谱,其范围大约为500 eV。X射线背景强到足以将IGM加热到~ 1000 K,并使几个百分比的中性氢蒸发。这些影响是重要的中性氢超精细过渡21厘米线签名的理解,Ly α森林,和光学厚度的CMB汤姆逊散射。

英文摘要:

Due to their long mean free paths, X-rays are expected to have many significant impacts globally on the properties of the intergalactic medium (IGM) by their heating and ionizing processes on large scales. At high redshifts, X-rays from Population (Pop) III binaries might have important effects on cosmic reionization and the Lyman alpha forest. As a continuation of our previous work on Pop III binary X-rays (Xu et al. 2014), we use the Pop III distribution and evolution from the Renaissance Simulations, a suite of self-consistent cosmological radiation hydrodynamics simulations of the formation of the first galaxies, to calculate the X-ray luminosity density and background over the redshift range 20 > z > 7.6. As we find that Pop III star formation continues at a low, nearly constant rate to the end of reionization, X-rays are being continuously produced at significant rates compared to other possible X-ray sources, such as AGNs and normal X-ray binaries during the same period of time. We estimate that Pop III binaries produce approximately 6 eV of energy in the X-rays per hydrogen atom. We calculate the X-ray background for different monochromatic photon energies. KeV X-rays redshift and accumulate to produce a strong X-ray background spectrum extending to roughly 500 eV. The X-ray background is strong enough to heat the IGM to ~ 1000 K and to ionize a few percent of the neutral hydrogen. These effects are important for an understanding of the neutral hydrogen hyperfine transition 21-cm line signatures, the Ly alpha forest, and optical depth of the CMB to Thomson scattering.

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