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arXiv 1505.04418astro-ph.HE
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FSRQ能产生IceCube探测到的弥散中微子发射吗?

Can FSRQs produce the IceCube detected diffuse neutrino emission?

Bin Wang, Zhuo Li

摘要:

冰立方曾报道探测到TeV-PeV中微子的弥散辐射,而平谱射电类星体(FSRQs)被认为是其候选源。假设FSRQs的中微子通量与其γ射线通量成正比,由FSRQs的Fermi-LAT测量得到的γ射线通量和IceCube探测到的中微子通量得到γ射线/中微子通量比。我们将这个比例应用于单个FSRQ,从而预测它们的中微子通量。我们发现,在冰立方点源搜索中,来自北方天空的大部分候选FSRQs预测的中微子通量高于冰立方上限;并且对于冰立方堆叠搜索中微子的样本,预测的堆叠通量甚至比堆叠通量的上限大几个数量级。因此,IceCube的叠加搜索极限,结合费米-LAT观测,已经拒绝了FSRQ作为IceCube探测到的扩散中微子的主要来源:根据整个(北部)天空的叠加搜索,FSRQ只能占IceCube探测到的扩散中微子通量的<10%(4%)。导出的中微子/γ射线通量比<<1,也意味着FSRQs的γ射线发射不能由次级轻子和来自π介子产生过程的光子产生。在假设的告诫进行了讨论。

英文摘要:

IceCube has reported the detection of a diffuse TeV-PeV neutrino emission, for which the flat spectrum radio quasars (FSRQs) have been proposed to be the candidate sources. Here we assume that the neutrino flux from FSRQs is proportional to their gamma-ray ones, and obtain the gamma-ray/neutrino flux ratio by the diffuse gamma-ray flux from Fermi-LAT measurement of FSRQs and the diffuse neutrino flux detected by IceCube. We apply this ratio to individual FSRQs and hence predict their neutrino flux. We find that a large fraction of candidate FSRQs from the northern sky in the IceCube point source search has predicted neutrino flux above the IceCube upper limit; and for the sample of stacking search for neutrinos by IceCube, the predicted stacked flux is even larger than the upper limit of stacked flux by orders of magnitude. Therefore the IceCube limit from stacking searches, combined with the Fermi-LAT observations, already rejects FSRQs as the main sources of IceCube-detected diffuse neutrinos: FSRQs can only account for <10% (4%) of the IceCube-detected diffuse neutrino flux, according to the stacking searches from the whole (northern) sky. The derived neutrino/gamma-ray flux ratio is <<1, also implying that the gamma-ray emission from FSRQs cannot be produced by the secondary leptons and photons from the pion production processes. The caveat in the assumptions is discussed.

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