标题： X射线偏振在相对论喷流中 显示英文标题

标题： X-ray Polarization in Relativistic Jets

摘要： 我们使用蒙特卡罗模拟研究活动星系核（AGN）中相对论喷流产生的康普顿化X射线的偏振特性。 我们考虑了AGN中观测到的X射线辐射的三种常见情景：来自吸积盘的黑体光子的康普顿散射；宇宙微波背景（CMB）光子的散射；以及由喷流电子发出的固有偏振同步辐射光子的自康普顿化。 我们的模拟显示，对于盘和CMB光子的康普顿化，散射光子的偏振度随着相对于喷流轴的观测倾斜角增加而增加。 在这两种情况下，最大线性偏振度约为20%。 在同步辐射自康普顿化（SSC）的情况下，我们发现所产生的X射线偏振强烈依赖于种子同步辐射光子注入的位置，当同步辐射发射集中在喷流基部附近时，典型的偏振分数约为P = 10 - 20%，而当同步辐射在整个喷流中均匀发射时，P = 20 - 70%。 这些结果表明，X射线偏振测量可能能够提供独特的线索，以确定相对论喷流中粒子加速区域的位置。 特别是，如果同步辐射光子在喷流中几乎均匀地发射，那么观测到的X射线偏振度可能对于每种竞争的X射线辐射机制（同步辐射、SSC或外部康普顿化）足够不同，从而确定哪种是主要过程。 然而，仅靠X射线偏振测量很可能无法区分盘和CMB康普顿化。 显示英文摘要

摘要： We investigate the polarization properties of Comptonized X-rays from relativistic jets in Active Galactic Nuclei (AGN) using Monte Carlo simulations. We consider three scenarios commonly proposed for the observed X-ray emission in AGN: Compton scattering of blackbody photons emitted from an accretion disk; scattering of cosmic microwave background (CMB) photons; and self-Comptonization of intrinsically polarized synchrotron photons emitted by jet electrons. Our simulations show that for Comptonization of disk and CMB photons, the degree of polarization of the scattered photons increases with the viewing inclination angle with respect to the jet axis. In both cases the maximum linear polarization is approximately 20%. In the case of synchrotron self-Comptonization (SSC), we find that the resulting X-ray polarization depends strongly on the seed synchrotron photon injection site, with typical fractional polarizations of approximately P = 10 - 20% when synchrotron emission is localized near the jet base, while P = 20 - 70% for the case of uniform emission throughout the jet. These results indicate that X-ray polarimetry may be capable of providing unique clues to identify the location of particle acceleration sites in relativistic jets. In particular, if synchrotron photons are emitted quasi-uniformly throughout a jet, then the observed degree of X-ray polarization may be sufficiently different for each of the competing X-ray emission mechanisms (synchrotron, SSC or external Comptonization) to determine which is the dominant process. However, X-ray polarimetry alone is unlikely to be able to distinguish between disk and CMB Comptonization.