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arXiv 0907.1741astro-ph.HEastro-ph.CO
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未分辨离散源对河外Gamma-Ray背景的贡献(EGRB)

Contribution from unresolved discrete sources to the Extragalactic Gamma-Ray Background (EGRB)

D. Bhattacharya, P. Sreekumar, R. Mukherjee

摘要:

河外伽马射线背景(EGRB)的起源仍然是一个悬而未决的问题,即使在它被发现近40年之后。排放可能来自真正的扩散过程,也可能来自未解决的点源。虽然EGRET(高能伽马射线实验望远镜)探测到的271个点源中的大多数都是未知的,但在已识别的源中,耀变体是主要的候选者。因此,未解决的耀变体可能被认为是EGRB的主要贡献者,并且已经进行了许多研究来了解它们的分布,演化和对EGRB的贡献。考虑到伽玛射线辐射主要来自耀变体的喷流,并且喷流辐射随喷流与视线角的增大而迅速减小,EGRET无法探测到许多大倾角的活动星系核(AGN)也就不足为奇了。虽然费米望远镜在前三个月的巡天中只能探测到少数几个大倾角活动星系核,但在不久的将来,它有望探测到许多这样的源。由于非耀变体活动星系核的密度比耀变体高,它们也可能对EGRB有重要贡献。本文讨论了正常星系、星暴星系、耀变体和离轴活动星系核等未分辨离散源对EGRB的贡献。

英文摘要:

The origin of the extragalactic gamma-ray background (EGRB) is still an open question, even after nearly forty years of its discovery. The emission could originate from either truly diffuse processes or from unresolved point sources. Although the majority of the 271 point sources detected by EGRET (Energetic Gamma Ray Experiment Telescope) are unidentified, of the identified sources, blazars are the dominant candidates. Therefore, unresolved blazars may be considered the main contributor to the EGRB, and many studies have been carried out to understand their distribution, evolution and contribution to the EGRB. Considering that gamma-ray emission comes mostly from jets of blazars and that the jet emission decreases rapidly with increasing jet to line-of-sight angle, it is not surprising that EGRET was not able to detect many large inclination angle active galactic nuclei (AGNs). Though Fermi could only detect a few large inclination angle AGNs in the first three months' survey, it is expected to detect many such sources in the near future. Since non-blazar AGNs are expected to have higher density as compared to blazars, these could also contribute significantly to the EGRB. In this paper we discuss contributions from unresolved discrete sources including normal galaxies, starburst galaxies, blazars and off-axis AGNs to the EGRB.

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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