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arXiv 0810.3764astro-ph
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射电星系中热点的NIR/光学对应物

NIR/Optical Counterparts of Hotspots in Radio Galaxies

K. -H. Mack, M. A. Prieto, G. Brunetti, M. Orienti

摘要:

我们提出了新的高空间分辨率VLT和VLA观测的样本9个低功率(P_{1.4 GHz} < 10^{25} W/Hz)的无线电热点。在9个观测对象中,有4个明确检测到红外/光学发射,检测率至少为45%。这种辐射被解释为来自在热点加速的电子的同步辐射。这些热点的综合光谱揭示了10^5和10^6 GHz之间的典型断裂频率,比通常在高功率热点中发现的高两个数量级。这支持了这样一种观点,即在磁场强度相对较低的低功率热点中,电子以较高的频率发射其大部分能量。一个简单的光谱老化分析将意味着发射电子已经注入热点体积不到10^3年前。我们讨论了可能的情况,以解释缺乏较老的电子在热点区域。特别是,扩展形态的近红外/光发射将表明,有效的再加速机制,使电子种群。

英文摘要:

We present new high spatial resolution VLT and VLA observations of a sample of nine low-power (P_{1.4 GHz} < 10^{25} W/Hz) radio hotspots. Infrared/optical emission is definitely detected in four of the nine observed objects, resulting in a detection rate of at least 45%. This emission is interpreted as synchrotron radiation from the electrons accelerated in the hot spots. The integrated spectra of these hotspots reveal typical break frequencies between 10^5 and 10^6 GHz, two orders of magnitude higher than typically found in high-power hotspots. This supports the idea that in low-power hotspots with their relatively low magnetic field strengths electrons emit most of their energy at higher frequencies. A simple spectral ageing analysis would imply that the emitting electrons have been injected into the hotspot volume less than ~10^3 years ago. We discuss possible scenarios to explain the lack of older electrons in the hotspot region. In particular, the extended morphology of the NIR/optical emission would suggest that efficient re-acceleration mechanisms rejuvenate the electron populations.

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