IMPLICATIONS OF FERMI OBSERVATIONS FOR HADRONIC MODELS OF RADIO HALOS IN CLUSTERS OF GALAXIES
IMPLICATIONS OF FERMI OBSERVATIONS FOR HADRONIC MODELS OF RADIO HALOS IN CLUSTERS OF GALAXIES
复制标题
费米观测对星系团射电晕强子模型的影响
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
S. Profumo
中科院分区：
文献类型：
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作者：
T. Jeltema;S. Profumo
我们分析了费米探测不到星系团的γ射线辐射对星系团射电晕起源的强子模型的影响。在强子模型中，非弹性质子-质子碰撞产生了电子-正电子，为观测到的同步辐射提供了能量，产生了来自中性π介子衰变的伽马射线通量，其光谱和归一化取决于观测到的射电发射率和星团磁场。因此，我们推断平均集群磁场的强子模型的费米伽玛射线极限的下限。我们还计算了宇宙线的最大能量密度和强子射电晕模型的最小保证γ射线通量。我们发现，观测上最有趣的情况下对应的集群具有大的无线电发射率具有软谱。对这些星系团中心磁场值的估计大于或接近于从星系团的法拉第旋转测量中推断出的最大磁场值，这使得射电晕的强子起源变得紧张。然而，在大多数情况下，我们发现费米数据本身并不排除强子模型集群无线电晕的预期伽马射线通量可以被推到费米灵敏度以下的渐近大磁场。我们还发现，宇宙射线并没有显着的集群能量预算附近的射电晕集群。
We analyze the impact of the Fermi non-detection of gamma-ray emission from clusters of galaxies on hadronic models for the origin of cluster radio halos. In hadronic models, the inelastic proton–proton collisions responsible for the production of the electron–positron population fueling the observed synchrotron radio emission yield a gamma-ray flux, from the decay of neutral pions, whose spectrum and normalization depend on the observed radio emissivity and on the cluster magnetic field. We thus infer lower limits on the average cluster magnetic field in hadronic models from the Fermi gamma-ray limits. We also calculate the corresponding maximal energy density in cosmic rays and the minimal-guaranteed gamma-ray flux from hadronic radio-halo models. We find that the observationally most interesting cases correspond to clusters with large radio emissivities featuring soft spectra. Estimates of the central magnetic field values for those clusters are larger than, or close, to the largest magnetic field values inferred from Faraday rotation measures of clusters, placing tension on the hadronic origin of radio halos. In most cases, however, we find that the Fermi data do not per se rule out hadronic models for cluster radio halos as the expected gamma-ray flux can be pushed below the Fermi sensitivity for asymptotically large magnetic fields. We also find that cosmic rays do not contribute significantly to the cluster energy budget for nearby radio-halo clusters.
DOI：
10.1007/978-1-4020-6941-3_8
发表时间：
2008
期刊：
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影响因子：
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作者：
Birkinshaw M
通讯作者：
Birkinshaw M