Constraints on the multi-TeV particle population in the Coma galaxy cluster with HESS observations
Constraints on the multi-TeV particle population in the Coma galaxy cluster with HESS observations
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DOI：
10.1051/0004-6361/200912086
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发表时间：
2009-08-01
影响因子：
6.5
通讯作者：
Zech, A.
中科院分区：
文献类型：
--
作者：
Aharonian, F.;Akhperjanian, A. G.;Zech, A.
目标。星系团是寻找超高能粒子加速器的关键目标。后发星团因其质量大、距离近以及以星团核心为中心的非热射电发射而成为此类搜索的最佳候选者之一。方法。 HESS（高能立体系统）望远镜对后发彗发进行了大约 8 小时的观察，以寻找能量 > 1 TeV 的伽马射线发射。 HESS 的 3.5 度 FWHM 大视场非常适合观察各种尺寸的一系列目标，包括后发星团核心、西南方向的射电遗迹 (1253+275) 和合并/坠落 (NGC 4839) 区域，并且具有大于 1 度的特征。结果。没有发现点状或扩展 TeV 伽马射线发射的证据，并且为后发区核心和其他区域设置了 E > 1、> 5 和 > 10 TeV 的 TeV 通量 F(E) 上限。将这些限制转换为能量通量 (EF)-F-2(E) 时，最低或最具约束力的是后发核心的 E > 5 TeV 上限（0.2 度半径），类似于 8% Crab 通量单位或类似于 10(-13) ph cm(-2) s(-1)。结论。将后发堆核心的上限与质子-质子相互作用产生的伽马射线发射的预测进行了比较，其水平最终与后发簇团的质量成比例。使用我们最严格的 E > 5 TeV 限制，对具有注入能谱 alpha E-2.1 的非热质子的总能量含量和簇中热气体之后的空间分布进行直接约束，发现类似于热能的 0.2 倍，或类似于 10(62) erg。在这种情况下，E > 5 TeV 伽马射线阈值对应于大于或类似于 50 TeV 的宇宙射线质子能量。我们的上限排除了星团伽马射线发射的最乐观的理论模型，并补充了射电观测，这些观测将星团中的宇宙射线含量限制在明显较低的质子能量下，但受到磁场强度假设的影响。
Aims. Galaxy clusters are key targets in the search for ultra high energy particle accelerators. The Coma cluster represents one of the best candidates for such a search owing to its high mass, proximity, and the established non-thermal radio emission centred on the cluster core.Methods. The HESS (High Energy Stereoscopic System) telescopes observed Coma for similar to 8 h in a search for gamma-ray emission at energies > 1 TeV. The large 3.5 degrees FWHM field of view of HESS is ideal for viewing a range of targets at various sizes including the Coma cluster core, the radio-relic (1253+275) and merger/infall (NGC 4839) regions to the southwest, and features greater than 1 degrees away.Results. No evidence for point-like nor extended TeV gamma-ray emission was found and upper limits to the TeV flux F(E) for E > 1, > 5, and > 10 TeV were set for the Coma core and other regions. Converting these limits to an energy flux (EF)-F-2(E) the lowest or most constraining is the E > 5 TeV upper limit for the Coma core (0.2 degrees radius) at similar to 8% Crab flux units or similar to 10(-13) ph cm(-2) s(-1).Conclusions. The upper limits for the Coma core were compared with a prediction for the gamma-ray emission from proton-proton interactions, the level of which ultimately scales with the mass of the Coma cluster. A direct constraint using our most stringent limit for E > 5 TeV, on the total energy content in non-thermal protons with injection energy spectrum alpha E-2.1 and spatial distribution following the thermal gas in the cluster, is found to be similar to 0.2 times the thermal energy, or similar to 10(62) erg. The E > 5 TeV gamma-ray threshold in this case corresponds to cosmic-ray proton energies greater than or similar to 50 TeV. Our upper limits rule out the most optimistic theoretical models for gamma ray emission from clusters and complement radio observations which constrain the cosmic ray content in clusters at significantly lower proton energies, subject to assumptions on the magnetic field strength.