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arXiv 0907.0727astro-ph.COastro-ph.HE
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H.E.S.S.对后发星系团中multi-TeV粒子布居的约束意见

Constraints on the multi-TeV particle population in the Coma Galaxy Cluster with H.E.S.S. observations

The HESS Collaboration, F. A. Aharonian

摘要:

H.E.S.S. (High能量立体系统(英语:Energy Stereoscopic System)的望远镜对后发座进行了约8小时的观测,以寻找能量大于1 TeV的伽马射线辐射。H.E.S.S.的3.5 ° FWHM大视场对于观察各种大小的目标是理想的,包括后发座星系团核心,西南部的射电遗迹(1253+275)和合并/坠落(NGC 4839)区域,以及大于度的特征。没有发现点状或扩展TeV伽马射线发射的证据,并且在后发座核心和其他区域设定了E>1、>5和> 10 TeV的TeV通量F(E)的上限。将这些极限转换为能通量E^2F(E),最低或最大的限制是后发座核心(半径为0.2度)在~ 8 Crab通量单位或~10^{-13}ph cm^{-2} s^{-1}时E> 5 TeV的上限。后发座核心的上限与质子-质子相互作用的伽马射线发射预测进行了比较,其水平最终与后发座星系团的质量成比例。使用我们对E>5 TeV的最严格限制,对注入能谱与E^{-2.1}成比例且空间分布遵循团簇中热气体的非热质子的总能量含量的直接约束被发现为~0.2倍的热能,或~10^{62}erg。在这种情况下,E>5 TeV的伽马射线阈值对应于宇宙射线质子能量> 50 TeV。我们的上限排除了最乐观的理论模型的γ射线发射的集群和补充无线电观测,约束宇宙射线的内容在集群中显着较低的质子能量,受假设的磁场强度。

英文摘要:

The H.E.S.S. (High Energy Stereoscopic System) telescopes observed Coma for ~8hr in a search for gamma-ray emission at energies >1TeV. The large 3.5deg FWHM field of view of H.E.S.S. 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 deg away. 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 >10TeV were set for the Coma core and other regions. Converting these limits to an energy flux E^2F(E) the lowest or most constraining is the E>5TeV upper limit for the Coma core (0.2deg radius) at ~8Crab flux units or ~10^{-13}ph cm^{-2} s^{-1}. 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 proportional to E^{-2.1} and spatial distribution following the thermal gas in the cluster, is found to be ~0.2 times the thermal energy, or ~10^{62}erg. The E>5 TeV gamma-ray threshold in this case corresponds to cosmic-ray proton energies >50TeV. 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.

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