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arXiv 1801.09683astro-ph.HE
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宇宙时间内恒星形成星系中高能gamma-ray和中微子的产生:解释IceCube数据的困难

High-energy gamma-ray and neutrino production in star-forming galaxies across cosmic time: Difficulties in explaining the IceCube data

Takahiro Sudoh, Tomonori Totani, Norita Kawanaka

摘要:

本文提出了一个新的理论模型,从恒星形成速率($ψ$)、气体质量($M_{\rm gas}$)、恒星质量和星系盘大小出发,考虑了宇宙射线的产生、传播和相互作用,预测了恒星形成星系的γ射线和中微子辐射的光度和光谱。与简单的幂律模型相比,该模型更好地再现了观测到的由{ \it Fermi}探测到的邻近星系的γ射线光度作为$ψ$或$ψM_{\rm gas}$的函数。然后,利用一个半解析宇宙学星系形成模型,再现了许多观测到的局域星系和高红移星系的数量,用该模型预测了来自恒星形成星系的宇宙背景γ射线和中微子通量。使用附近星系的伽马射线光度校准模型使我们能够做出比以前的研究更可靠的预测。在我们的基线模型中,恒星形成星系产生约20%的各向同性伽马射线背景,不能被{ \it费米}分辨,只有0.5%的冰立方中微子。即使在一个极端的模型中,假设所有星系的硬注入宇宙射线光谱指数为2.0,最多也只能解释22%的冰立方中微子。这些结果表明,很难用恒星形成星系来解释大多数冰立方中微子,而不违反附近星系的伽马射线约束。

英文摘要:

We present a new theoretical modeling to predict luminosity and spectrum of gamma-ray and neutrino emission of a star-forming galaxy, from star formation rate ($ψ$), gas mass ($M_{\rm gas}$), stellar mass, and disk size, taking into account production, propagation and interactions of cosmic rays. The model reproduces the observed gamma-ray luminosities of nearby galaxies detected by {\it Fermi} better than the simple power-law models as a function of $ψ$ or $ψM_{\rm gas}$. Then this model is used to predict the cosmic background flux of gamma-ray and neutrinos from star-forming galaxies, by using a semi-analytical model of cosmological galaxy formation that reproduces many observed quantities of local and high-redshift galaxies. Calibration of the model using gamma-ray luminosities of nearby galaxies allows us to make a more reliable prediction than previous studies. In our baseline model star-forming galaxies produce about 20% of isotropic gamma-ray background unresolved by {\it Fermi}, and only 0.5% of IceCube neutrinos. Even with an extreme model assuming a hard injection cosmic-ray spectral index of 2.0 for all galaxies, at most 22% of IceCube neutrinos can be accounted for. These results indicate that it is difficult to explain most of IceCube neutrinos by star-forming galaxies, without violating the gamma-ray constraints from nearby galaxies.

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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