标题： 从稳定性分析推导S5 0836+710喷流的物理参数 显示英文标题

标题： Derivation of the physical parameters of the jet in S5 0836+710 from stability analysis

摘要： 一些河外喷流在不同尺度上显示出周期性结构，这些结构可以与增长的不稳定性相关联。 发展中的不稳定性模式的波长及其比例取决于流动参数，因此研究这些结构有助于了解所涉及尺度上的喷流物理。 在本工作中，我们使用从S5 B0836$+$710的不同观测中获得的喷流脊线拟合，并应用相对论剪切流的稳定性分析来推导喷流的物理参数估计值。 基于观察到的结构是由增长的开尔文-亥姆霍兹（KH）不稳定性模式产生的假设，我们对相对论剪切喷流在不同喷流参数范围内进行了稳定性数值计算。 我们在喷流与周围介质密度比和喷流内部能量上覆盖了多个数量级，并检查了不同的洛伦兹因子和剪切层宽度的不同值。 这是一种独立的方法来获得喷流的物理参数估计值。 通过将计算给出的每个相关模式的最快增长波长与文献中报告的观测波长进行比较，我们得出了喷流洛伦兹因子、特定内部能量、喷流与周围介质密度比和马赫数的独立估计值。 我们得到一个喷流 洛伦兹因子$\gamma \simeq 12$，特定内部能量为$\varepsilon \simeq 10^{-2}\,c^2$，喷流与周围介质密度比为$\eta\approx 10^{-3}$，以及内部（经典）喷流马赫数为$M_\mathrm{j}\approx 12$。 我们还发现，通过具有宽度为$\simeq 10\,\%$的喷流半径的横向结构，波长比能得到更好的恢复。 这种方法是一种强大的工具，可用于所有显示螺旋图案且具有不同波长的喷流的喷流参数推导。 显示英文摘要

摘要： A number of extragalactic jets show periodic structures at different scales that can be associated with growing instabilities. The wavelengths of the developing instability modes and their ratios depend on the flow parameters, so the study of those structures can shed light on jet physics at the scales involved. In this work, we use the fits to the jet ridgeline obtained from different observations of S5 B0836$+$710 and apply stability analysis of relativistic, sheared flows to derive an estimate of the physical parameters of the jet. Based on the assumption that the observed structures are generated by growing Kelvin-Helmholtz (KH) instability modes, we have run numerical calculations of stability of a relativistic, sheared jet over a range of different jet parameters. We have spanned several orders of magnitude in jet-to-ambient medium density ratio, and jet internal energy, and checked different values of the Lorentz factor and shear layer width. This represents an independent method to obtain estimates of the physical parameters of a jet. By comparing the fastest growing wavelengths of each relevant mode given by the calculations with the observed wavelengths reported in the literature, we have derived independent estimates of the jet Lorentz factor, specific internal energy, jet-to-ambient medium density ratio and Mach number. We obtain a jet Lorentz factor $\gamma \simeq 12$, specific internal energy of $\varepsilon \simeq 10^{-2}\,c^2$, jet-to-ambient medium density ratio of $\eta\approx 10^{-3}$, and an internal (classical) jet Mach number of $M_\mathrm{j}\approx 12$. We also find that the wavelength ratios are better recovered by a transversal structure with a width of $\simeq 10\,\%$ of the jet radius. This method represents a powerful tool to derive the jet parameters in all jets showing helical patterns with different wavelengths.