星系团中硬X射线过剩的ICS解释：蛇夫座星系
On the ICS interpretation of the Hard X-Ray Excesses in Galaxy Clusters: the case of Ophiuchus
摘要：
在星系团中，高E电子通过CMB光子的逆康普顿散射（ICS）产生硬X射线（HXR）辐射。我们推导了在初级宇宙线模型、次级宇宙射线模型和中性伴子DM湮灭模型下蛇夫座的ICS HXR辐射。我们进一步讨论了集团大气的变暖射线模型的预测。在拟合观测到的HXR辐射的假设下，我们发现高E电子对团簇大气的影响是多方面的：（1）如果初始电子的光谱截止于E~30（90）MeV，谱指数为3.5，则初始电子的光谱可以与观测数据勉强一致（4.4）; ii）来自pp碰撞的次级电子模型与γ射线极限不一致，宇宙射线质子对离子束气体的加热作用过大，它们在团中心的压力大大超过了热力学压力; iii）来自DM湮灭的次级电子模型与伽马射线和无线电极限不一致，并且电子在团簇中心处对IC气体产生太多的加热，除非中性伴子湮灭截面远低于建议值。我们的结论是，ICS的次级电子从中性伴DM湮灭和pp碰撞不能负责的机制HXR过量发射;初级电子仍然是一个勉强可行的解决方案，提供他们的光谱具有低能量截止在E~30-90 MeV。到目前为止，WR模型在温度分布、加热、压力和光谱能量分布方面提供了对星团的最佳描述。费米对蛇夫座的观测将进一步限制这个模型。
英文摘要：
(Abridged) High-E electrons produce Hard X-Ray (HXR) emission in galaxy clusters by via Inverse Compton Scattering (ICS) of CMB photons. We derive the ICS HXR emission of Ophiuchus under various scenarios: primary cosmic ray model, secondary cosmic rays model and neutralino DM annihilation scenario. We further discuss the predictions of the Warming Ray model for the cluster atmosphere. Under the assumption to fit the observed HXR emission, we find that the high-E electrons induce various consequences on the cluster atmosphere: i) primary electrons can be marginally consistent with the data provided that their spectrum is cutoff at E~30(90) MeV for spectral index of 3.5 (4.4); ii) secondary electron models from pp collisions are inconsistent with gamma-ray limits, cosmic ray protons produce too much heating of the IC gas and their pressure at the cluster center largely exceeds the thermal one; iii) secondary electron models from DM annihilation are inconsistent with gamma-ray and radio limits and electrons produce too much heating of the IC gas at the cluster center, unless the neutralino annihilation cross section is much lower than the proposed value. We conclude that ICS by secondary electrons from both neutralino DM annihilation and pp collisions cannot be the mechanism responsible for the HXR excess emission; primary electrons are still a marginally viable solution provided that their spectrum has a low-energy cutoff at E~30-90 MeV. The WR model offers, so far, the best description of the cluster in terms of temperature distribution, heating, pressure and spectral energy distribution. Fermi observations of Ophiuchus will set further constraints to this model.
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