Probing the cosmic-ray content of galaxy clusters by stacking Fermi-LAT count maps
Probing the cosmic-ray content of galaxy clusters by stacking Fermi-LAT count maps
复制标题
通过堆叠费米-LAT 计数图探测星系团的宇宙射线含量
DOI：
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
R. Walter
中科院分区：
文献类型：
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作者：
B. Huber;B. Huber;C. Tchernin;D. Eckert;C. Farnier;C. Farnier;A. Manalaysay;U. Straumann;R. Walter
目标。射电观测表明，星系团是宇宙射线（CR）的巨大储存库。虽然来自簇体积的伽马射线信号预计将通过CR质子与周围等离子体的相互作用而产生，但仍然缺少确认观察结果。方法.我们通过分析一组堆叠的费米-LAT计数图来寻找星系团方向上的累积伽马射线发射。此外，我们研究了冷核和非冷核团簇人口之间的排放可能存在的系统差异。结果利用从HIFLUGCS目录中选择的53个聚类的样本，我们没有从堆叠样本中检测到显著的信号。每个集群的总堆叠样品的平均通量的上限是在几个10 - 11 phcm-2 s-1的水平，在95%的置信水平在1-300 GeV的频带，假设幂律光谱与光子指数2.0，2.4，2.8和3.2。在样品中冷核和非冷核团簇的单独堆叠导致类似的值，分别为约5 × 1011 phcm 2 s-1和2 × 1011 phcm 2 s-1。结论.在假设CR与周围热气体碰撞产生的衰变π 0是γ射线发射的原因的情况下，我们对星系团中CR的平均含量设定了上限。对于整个星系团，我们对伽马射线通量的上限转化为光子指数为2.4时平均CR与热能比的上限为4.6%，尽管个别系统可能会超过这个限制。我们的95%上限是在数值模拟的预期水平，这可能表明，在宇宙学冲击注入CR的效率比以前假设的低。
Aims. Observation in radio have shown that galaxy clusters are giant reservoirs of cosmic rays (CR). Although a gammaray signal from the cluster volume is expected to arise through interactions of CR protons with the ambient plasma, a confirming observation is still missing. Methods. We search for a cumulative gamma-ray emission in direction of galaxy clusters by analysing a collection of stacked Fermi-LAT count maps. Additionally, we investigate possible systematic differences in the emission between cool-core and non-cool core cluster populations. Results. Making use of a sample of 53 clusters selected from the HIFLUGCS catalog, we do not detect a significant signal from the stacked sample. The upper limit on the average flux per cluster derived for the total stacked sample is at the level of a few 10 11 phcm 2 s 1 at 95% confidence level in the 1-300 GeV band, assuming power-law spectra with photon indices 2.0, 2.4, 2.8 and 3.2. Separate stacking of the cool core and non-cool core clusters in the sample lead to similar values of around 5 × 10 11 phcm 2 s 1 and 2 × 10 11 phcm 2 s 1 , respectively. Conclusions. Under the assumption that decaying π 0 , produced in collisions between CRs and the ambient thermal gas, are responsible for the gamma-ray emission, we set upper limits on the average CR content in galaxy clusters. For the entire cluster population, our upper limit on the gamma-ray flux translates into an upper limit on the average CR-to-thermal energy ratio of 4.6% for a photon index of 2.4, although it is possible for individual systems to exceed this limit. Our 95% upper limits are at the level expected from numerical simulations, which likely suggests that the injection of CR at cosmological shocks is less efficient than previously assumed.
AGN 反馈的热迹和非热迹：宇宙学 AMR 模拟的结果
影响因子：
4.8
作者：
Brüggen;Gheller
通讯作者：
Gheller
用费米大面积望远镜观测到的最亮星团星系的叠加分析
影响因子：
4.8
作者：
Dutson K
通讯作者：
Dutson K