High-energy neutrinos from FR0 radio galaxies?
High-energy neutrinos from FR0 radio galaxies?
复制标题
来自 FR0 射电星系的高能中微子？
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
G. Ghisellini
中科院分区：
文献类型：
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作者：
F. Tavecchio;C. Righi;A. Capetti;P. Grandi;G. Ghisellini
冰立方探测到的高能（100 TeV）中微子的发射源仍然未知。在可能的候选者中，经常检查具有相对论性喷流的活动星系核，因为流出的等离子体似乎提供了加速所需的母体高能宇宙射线的理想环境。由于没有探测到单点源，或者在冰立方事件中几乎同样没有发现来自同一天空位置的多胞胎，这限制了宇宙密度和这些源的中微子输出，表明存在大量微弱的源。在这里，我们探索了FR0射电星系的可能性，FR0射电星系是最近在大型射电和光学调查中发现的致密源种群，代表了大部分的射电大声AGN种群，可以代表中微子发射的合适候选者。对Fermi上的大面积望远镜最近探测到的与$\gamma$射线源有关的FR0射电星系的光谱能量分布进行了建模，得出了其射流的物理参数，特别是其携带的功率。我们考虑了中微子产生的可能机制，得出结论，质子和环境辐射之间的喷流中的p\gamma$反应效率太低，无法维持所需的输出。我们提出了一种替代方案，其中质子在喷流中加速，从喷流中逃逸并扩散到宿主星系，由于星际气体的散射而产生中微子，这与恒星形成星系中发生的过程非常相似。
The sources responsible for the emission of high-energy ($\gtrsim$ 100 TeV) neutrinos detected by IceCube are still unknown. Among the possible candidates, active galactic nuclei with relativistic jets are often examined, since the outflowing plasma seems to offer the ideal environment to accelerate the required parent high-energy cosmic rays. The non-detection of single point sources or -- almost equivalently -- the absence, in the IceCube events, of multiplets originating from the same sky position, constrains the cosmic density and the neutrino output of these sources, pointing to a numerous population of faint sources. Here we explore the possibility that FR0 radiogalaxies, the population of compact sources recently identified in large radio and optical surveys and representing the bulk of radio-loud AGN population, can represent suitable candidates for neutrino emission. Modeling the spectral energy distribution of a FR0 radiogalaxy recently associated to a $\gamma$-ray source detected by the Large Area Telescope onboard Fermi, we derive the physical parameters of its jet, in particular the power carried by it. We consider the possible mechanisms of neutrino production, concluding that $p\gamma$ reactions in the jet between protons and ambient radiation is too inefficient to sustain the required output. We propose an alternative scenario, in which protons, accelerated in the jet, escape from it and diffuse in the host galaxy, producing neutrinos as a result of $pp$ scattering with the interstellar gas, in strict analogy with the processes taking place in star-forming galaxies.