Physical Parameters in the Hot Spots and Jets of Compact Symmetric Objects
Physical Parameters in the Hot Spots and Jets of Compact Symmetric Objects
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紧凑对称物体热点和射流的物理参数
DOI：
10.1086/338882
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
J. Martí
中科院分区：
文献类型：
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作者：
M. Perucho;J. Martí
我们提出了一个模型，用于在同步加速器发射和最小能量条件等非常基本的假设下确定紧凑对称物体（CSO）样本的喷流和热点的物理参数。基于这个模型，我们为这些源提出了一个简单的演化场景，假设它们在与外部介质和恒定射流功率的冲压压力平衡中演化。我们模型的参数受到观测数据（无线电光度、热点半径和热点前进速度）与投影线性尺寸的拟合的限制。从这些图中，我们得出结论，CSO 的演化是自相似的，并且它们的射电光度随着第一个千秒差距的线性大小而增加。假设从运动学和热力学的角度来看，供给 CSO 的射流都是相对论性的，我们使用热点内的压力和粒子数密度值来估计这些相对论性射流的动量（推力）、能量和粒子的通量。以这种方式获得的平均射流功率与 Fanaroff-Riley 2 型源推断的功率在一个数量级内，这与 CSO 是大型双星的可能前体是一致的。对于重离子射流，推断的粒子通量相当于爱丁顿极限下 108 M☉ 黑洞吸积质量的约 10%，这表明吸积流可以非常有效地转化为喷射或射流的轻子成分。我们考虑了三种不同的模型（即模型 I、IIa 和 IIb）。模型 I 假设热点前进速度恒定且光度增加，但由于其能源成本而可以被排除。然而，模型 IIa 和 IIb 似乎描述了以恒定前进速度和降低光度（模型 IIa）以及降低热点前进速度和增加光度（模型 IIb）的源的限制行为。在我们所有的模型中，热点光度和前进速度与源线性尺寸的斜率仅由一个参数控制，即外部密度梯度。还包括对模型 IIa 和 IIb 的有效性的简短讨论，以描述强大的无线电源从 CSO 阶段的完整演变。
We present a model to determine the physical parameters of jets and hot spots of a sample of compact symmetric objects (CSOs) under very basic assumptions like synchrotron emission and minimum energy conditions. Based on this model, we propose a simple evolutionary scenario for these sources assuming that they evolve in ram pressure equilibrium with the external medium and constant jet power. The parameters of our model are constrained from fits of observational data (radio luminosity, hot spot radius, and hot spot advance speed) versus projected linear size. From these plots we conclude that CSOs evolve self-similarly and that their radio luminosity increases with linear size along the first kiloparsec. Assuming that the jets feeding CSOs are relativistic from both kinematical and thermodynamical points of view, we use the values of the pressure and particle number density within the hot spots to estimate the fluxes of momentum (thrust), energy, and particles of these relativistic jets. The mean jet power obtained in this way is within an order of magnitude of that inferred for Fanaroff-Riley type 2 sources, which is consistent with CSOs being the possible precursors of large doubles. The inferred flux of particles corresponds to, for a barionic jet, about 10% of the mass accreted by a black hole of 108 M☉ at the Eddington limit, pointing toward a very efficient conversion of accretion flow into ejection or to a leptonic composition of jets. We have considered three different models (namely, models I, IIa, and IIb). Model I, assuming constant hot spot advance speed and increasing luminosity, can be ruled out on the grounds of its energy cost. However, models IIa and IIb seem to describe limiting behaviors of sources evolving at constant advance speed and decreasing luminosity (model IIa) and decreasing hot spot advance speed and increasing luminosity (model IIb). In all our models the slopes of the hot spot luminosity and advance speed with source linear size are governed by only one parameter, namely, the external density gradient. A short discussion on the validity of models IIa and IIb to describe the complete evolution of powerful radio sources from their CSO phase is also included.