绘架座A西部热点X射线的起源和可能的GeV-TeV辐射
Origin of the X-rays and Possible GeV-TeV Emission from the Western Hot Spot Of Pictor A
摘要：
绘架座A是一个邻近的法那罗夫-莱利II类（FR II）射电星系，有一个明亮的热点，即西部热点。对热斑光辐射的高偏振观测表明，热斑光辐射可能是热斑中相对论电子的同步辐射。这些电子可能能够通过逆康普顿（IC）散射产生高能量伽马射线光子。我们使用单区和多区同步加速器+同步加速器自康普顿（SSC）模型来拟合从射电到热点的X射线波段的观测光谱能量分布（SED）。结果表明，在磁场强度比均分磁场弱得多的情况下，单区模型和多区模型都能拟合SED，但多区模型的拟合效果明显提高。这两个模型预测的热点作为一个GeV-TeV源，这可能是边缘检测费米/LAT和HESS。还考虑了宇宙微波背景（IC/CMB）的逆康普顿散射，但其对GeV-TeV辐射的贡献可以忽略不计。注意，在均分条件下，SED也可以用多区模型拟合，但预测的10^22 Hz通量太弱而无法检测。从这个FR II射电星系的TeV伽马射线的检测，如果得到证实，将建立一个新的子类的河外源在这个能量制度，因为大多数的活动星系核检测到的TeV能量的日期是高能量峰值BL湖对象。
英文摘要：
Pictor A is a nearby Fanaroff-Riley class II (FR II) radio galaxy with a bright hot spot, the western hot spot. Observation of high polarization in the optical emission of the hot spot indicates that the optical emission could be synchrotron radiation of relativistic electrons in the hot spot. These electrons may be able to produce high energy gamma-ray photons through inverse Compton (IC) scattering. We use single-zone and multi-zone synchrotron + synchrotron-self-Compton (SSC) models to fit the observed spectral energy distribution (SED) from the radio to the X-ray band of the hot spot. Our esults show that in the case of a much weaker magnetic field strength than the equipartition magnetic field, both the single-zone and multi-zone models can fit the SED, but the multi-zone model significantly improves the fit. The two models predict the hot spot as a GeV-TeV source, which might be marginally detectable with Fermi/LAT and HESS. The inverse Compton scattering of cosmic microwave background (IC/CMB) is also considered, but its contribution to GeV-TeV emission is negligible. Note that under the equipartition condition, the SED can also be fit with the multi-zone model, but the predicted flux at 10^22 Hz is too weak to be detectable. The detection of TeV gamma-rays from this FR II radio galaxy, if confirmed, would establish a new subclass of extragalactic source in this energy regime since most of the AGNs detected to date at TeV energies are high-energy-peaked BL Lac objects.
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