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arXiv 1102.1823astro-ph.CO
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X射线源的最近邻统计计数为II。钱德拉深场南

The nearest neighbor statistics for X-ray source counts II. Chandra Deep Field South

A. M. Soltan

摘要:

假设X射线背景(XRB)的未分辨部分由真正的漫射分量和低于当前检测阈值的弱源的总体组成。尽管这些弱源无法直接观察到,但可以通过统计方法来研究它们的集体性质。我们的目标是估计源计数低于传统的探测极限在钱德拉深场南2 Ms曝光。使用应用于光子计数分布的最近邻统计来评估源数目计数。该方法在这些系列的第一篇论文中进行了描述。源计数下降到3-4 × 10^{-18} cgs的软带(0.5-2 keV)和下降到2-3 × 10^{-17} cgs的硬带(2-8 keV)进行了评估。看来在软带中,源计数在低于~10^{-16} cgs时明显变陡。假设在10^{-16} - 10^{-14} cgs范围内的微分斜率b = -1.5至-1.6,则较弱源的数量表示近似的斜率。-2.0.在硬带中没有观察到陡峭化。软带中计数的陡化指示新的源群。一类中等红移的正常星系是一个自然的候选者。

英文摘要:

It is assumed that the unresolved fraction of the X-ray background (XRB) consists of a truly diffuse component and a population of the weak sources below the present detection threshold. Albeit these weak sources are not observed directly, their collective nature could be investigated by statistical means. The goal is to estimate the source counts below the conventional detection limit in the Chandra Deep Field-South 2Ms exposure. The source number counts are assessed using the nearest neighbor statistics applied to the distribution of photon counts. The method is described in the first paper of these series. The source counts down to 3-4 x 10^{-18} cgs in the soft band (0.5-2 keV) and down to 2-3 x 10^{-17} cgs in the hard band (2-8 keV) are evaluated. It appears that in the soft band the source counts steepen substantially below ~10^{-16} cgs. Assuming that the differential slope b = -1.5 to -1.6 in the range 10^{-16} - 10^{-14} cgs, the number of weaker sources indicates the slope of approx. -2.0. The steepening is not observed in the hard band. Steepening of counts in the soft band indicates a new population of sources. A class of normal galaxies at moderate redshifts is a natural candidate.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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