低光度射电星系喷流的相对论混合层模型
A relativistic mixing-layer model for jets in low-luminosity radio galaxies
摘要：
我们提出了一个分析模型的喷流在Fanaroff和Riley I类（FRI）射电星系，在最初的层流，相对论性流被包围的剪切层。我们应用适当的守恒定律来约束喷流参数，从观察到无线电发射突然变亮的模型开始。我们假设，在那里，射流充满了层流，并且从该点向外，与周围环境保持压力平衡。卷吸不断地将新的材料注入射流中并形成剪切层，该剪切层包含来自环境和层流核心的材料。剪切层随着距离迅速膨胀，直到最后核心消失，所有的材料都混合到剪切层中。超过这一点，剪切层扩展成锥形，并平稳减速。我们将我们的模型应用到观测良好的FRI源3C31，并表明存在自洽的解决方案。导出了射流功率、质量通量和卷吸率随离核距离的变化关系。预测的整体速度随距离的变化在外部的射流是在很好的协议与模型拟合VLA观测。我们对层状核心形状的预测可以用更高分辨率的成像进行测试。
英文摘要：
We present an analytical model for jets in Fanaroff & Riley Class I (FRI) radio galaxies, in which an initially laminar, relativistic flow is surrounded by a shear layer. We apply the appropriate conservation laws to constrain the jet parameters, starting the model where the radio emission is observed to brighten abruptly. We assume that the laminar flow fills the jet there and that pressure balance with the surroundings is maintained from that point outwards. Entrainment continuously injects new material into the jet and forms a shear layer, which contains material from both the environment and the laminar core. The shear layer expands rapidly with distance until finally the core disappears, and all of the material is mixed into the shear layer. Beyond this point, the shear layer expands in a cone and decelerates smoothly. We apply our model to the well-observed FRI source 3C31 and show that there is a self-consistent solution. We derive the jet power, together with the variations of mass flux and and entrainment rate with distance from the nucleus. The predicted variation of bulk velocity with distance in the outer parts of the jets is in good agreement with model fits to VLA observations. Our prediction for the shape of the laminar core can be tested with higher-resolution imaging.
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