Canonical Particle Acceleration in FR I Radio Galaxies
Canonical Particle Acceleration in FR I Radio Galaxies
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FR I 射电星系中的规范粒子加速
DOI：
10.1086/430107
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
K. Makishima
中科院分区：
文献类型：
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作者：
A. Young;L. Rudnick;D. Katz;T. Delaney;N. Kassim;K. Makishima
匹配分辨率的多频VLA观测的四个射电星系的相对论电子分布的渐近低能斜率。当可用时，低能量斜率也被确定为文献中的其他来源。它们提供了独立于辐射和其他损失的加速物理学信息，这些信息混淆了大多数无线电，光学和X射线研究中的同步加速器光谱测量。我们发现一个狭窄的范围内推断的低能量电子能量斜率n（E）-2.1目前小样本的低光度源分类为FR I（不是经典的双打）。这个分布接近于，但显然不一致，试验粒子的极限n（E）= E-2.0预期从强扩散激波加速在非相对论性的限制。相对论激波或那些被有效加速的宇宙射线的背压所改变的激波是产生稍微陡峭的光谱的两种选择。我们注意到进一步研究的可能性，通过冲击，湍流，或剪切的耀斑和增亮区域FR I喷流，因为它们远离核加速。喷流在秒差距尺度和准直喷流和热点FR II（经典双）源将由不同的加速网站和机制，他们似乎显示出更广泛的频谱范围比FR I源。
Matched-resolution multifrequency VLA observations of four radio galaxies are used to derive the asymptotic low-energy slope of the relativistic electron distribution. When available, low-energy slopes are also determined for other sources in the literature. They provide information on the acceleration physics independent of radiative and other losses, which confuse measurements of the synchrotron spectra in most radio, optical, and X-ray studies. We find a narrow range of inferred low-energy electron energy slopes n(E) ∝ E-2.1 for the currently small sample of lower luminosity sources classified as FR I (not classical doubles). This distribution is close to, but apparently inconsistent with, the test particle limit of n(E) ∝ E-2.0 expected from strong diffusive shock acceleration in the nonrelativistic limit. Relativistic shocks or those modified by the back-pressure of efficiently accelerated cosmic rays are two alternatives to produce somewhat steeper spectra. We note for further study the possibility of acceleration through shocks, turbulence, or shear in the flaring and brightening regions in FR I jets as they move away from the nucleus. Jets on parsec scales and the collimated jets and hot spots of FR II (classical double) sources would be governed by different acceleration sites and mechanisms; they appear to show a much wider range of spectra than those for FR I sources.