半人马座A喷流纽结动力学和粒子加速的长期监测
Long Term Monitoring of the Dynamics and Particle Acceleration of Knots in the Jet of Centaurus A
摘要：
我们提出了新的和档案的多频无线电和X射线数据半人马座A获得了近20年的VLA和钱德拉，我们测量的X射线和无线电频谱指数的喷流结，通量密度变化的喷流结，偏振变化和自行车。我们比较观察到的属性与当前结形成模型和粒子加速机制。我们排除了脉冲粒子加速作为所有结的形成机制，因为我们在所有观测中检测到相同的结群，并且我们没有发现X射线结极端可变性的证据。我们发现最有可能的机制，所有的固定结是碰撞导致的局部冲击，其次是一个稳定的状态，长期的，稳定的粒子加速和X射线同步辐射。在这种情况下，只有X射线的节点具有太微弱而无法检测到的无线电对应物，而只有无线电的节点是由于没有粒子加速到X射线发射能量的弱冲击。虽然基结是约束激波的主要候选者，但在这附近存在一个移动的结以及存在两个基结的事实在这个模型中很难解释。我们检测到明显的运动在三节，但是，他们的速度和位置提供了没有决定性的证据，或反对一个更快的移动“脊柱”内的射流。静止和移动的仅无线电结可能是由于流体的压缩。
英文摘要：
We present new and archival multi-frequency radio and X-ray data for Centaurus A obtained over almost 20 years at the VLA and with Chandra, with which we measure the X-ray and radio spectral indices of jet knots, flux density variations in the jet knots, polarization variations, and proper motions. We compare the observed properties with current knot formation models and particle acceleration mechanisms. We rule out impulsive particle acceleration as a formation mechanism for all of the knots as we detect the same population of knots in all of the observations and we find no evidence of extreme variability in the X-ray knots. We find the most likely mechanism for all the stationary knots is a collision resulting in a local shock followed by a steady state of prolonged, stable particle acceleration and X-ray synchrotron emission. In this scenario, the X-ray-only knots have radio counterparts that are too faint to be detected, while the radio-only knots are due to weak shocks where no particles are accelerated to X-ray emitting energies. Although the base knots are prime candidates for reconfinement shocks, the presence of a moving knot in this vicinity and the fact that there are two base knots are hard to explain in this model. We detect apparent motion in three knots; however, their velocities and locations provide no conclusive evidence for or against a faster moving `spine' within the jet. The radio-only knots, both stationary and moving, may be due to compression of the fluid.
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