On the Relationship between BL Lacertae Objects and Fanaroff-Riley I Radio Galaxies
On the Relationship between BL Lacertae Objects and Fanaroff-Riley I Radio Galaxies
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BL 蜥蜴天体与 Fanaroff-Riley I 射电星系的关系
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发表时间：
1993
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影响因子：
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通讯作者：
G. Bicknell
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文献类型：
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作者：
G. Bicknell
本文结合NGC~315和NGC~6251这两个Firi射电星系的数据，验证了Fanaroff-Riley类射电星系含有洛伦兹因子为数量级的核心喷流，并且是BLLac天体的母族的观点。导出了卷吸相对论射流的守恒定律，并用它确定了初始相对论射流的马赫数与速度之间的关系。这种关系的一个直接结果是，如果一个最初的相对论喷流减速到一个跨音速马赫数，比如说0.5到1.5之间，那么它在这个点的速度在0.3到0.7倍光速之间。对NGC~315和NGC~6251的毫角秒和角秒数据的分析表明，在喷流压力不超过最低气压一个数量级的情况下，这些星系的核心喷流的洛伦兹因子可以高达2-4。如果喷气式飞机与视线成$sim 30度倾斜，这样的洛伦兹因子就更有可能，尽管也可能有更大的角度。对于核心洛伦兹因子在2-4范围内，喷流在大尺度上是温和相对论的，它们的速度与多普勒集束引起的喷流亮度不对称是一致的。如果是喷流平流产生的反向激波，则核心急流的显著射束所需的洛伦兹因子可以与核心中纽结的亚光速运动相协调。如果激波是正常的，中等急流洛伦兹因子是可能的，如果激波是倾斜的，则可能是更高的洛伦兹因子。这篇论文支持了这样一种观点，即在周五/II休息期从双面到单面射流的转变是由于
The idea that Fanaroff-Riley Class~I Radio Galaxies contain core jets with Lorentz factors of the order of a few and are the parent population for BL~Lac Objects is examined, with particular reference to the data on two FRI Radio Galaxies, NGC~315 and NGC~6251. Conservation laws for an entraining relativistic jet are derived and are used to determine a relationship between Mach number and velocity for initially relativistic jets. One immediate consequence of this relationship is that, if an initially relativistic jet is decelerated to a transonic Mach number between, say 0.5 and 1.5, then its velocity at this point is between 0.3 and 0.7 times the speed of light. Analysis of the milliarcsecond and arcsecond data on NGC~315 and NGC~6251 shows that the Lorentz factors of the core jets in these galaxies can be as high as 2-4 provided that the jet pressures are not much more than an order of magnitude higher than the minimum pressures. Such Lorentz factors are more plausible if the jets are inclined at $sim 30$ degrees to the line of sight, although larger angles would also be possible. For core Lorentz factors in the range 2-4, the jets are mildly relativistic on the large scale and their velocities are consistent with the jet brightness asymmetries being caused by Doppler beaming. The Lorentz factors required for significant beaming of core jets may be reconciled with subluminal motions of knots in the core if these are reverse shocks advected by the jet. Moderate jet Lorentz factors are possible if the shocks are normal and higher Lorentz factors are possible if the shocks are oblique. This paper provides support for the idea that the transition from two-sided to one-sided jets across the FRI/II break is due to the transition from