3C_（84）的1秒差距热斑与环境介质相互作用产生的偏振辐射增强
Enhanced Polarized Emission from the One-Parsec-Scale Hotspot of 3C 84 as a Result of the Interaction with Clumpy Ambient Medium
摘要：
本文介绍了在43 $\sim$ GHz的3C $\sim$ 84（NGC $\sim$ 1275）最内侧喷流的甚长基线阵列偏振观测。一个显着的偏振发射被检测到在热点的最里面的重新启动喷流，这是位于$\sim$ 1 pc以南的无线电核心。虽然上一份报告在西翼的南端提出了一个热点，但热点位置已被移至东翼的南端。法拉第旋转检测在43 GHz频带的整个带宽内。测量的旋转测量（RM）最多为（6.3 $\pm$ 1.9）$\times10^{5}$ $\sim$ rad $\sim$ m $^{-2}$，并且可能在一个月的时间尺度上略微随时间变化几倍。我们测得的RM和RM先前报告的CARMA和SMA观测不能一致地解释球形吸积流与幂律配置文件。我们建议，cluberous/不均匀的环境介质是负责所观察到的旋转措施。利用均分磁场，我们导出了$2\times10^{4}$ $\sim$ cm $^{-3}$的电子密度.这样的电子密度与中央发动机周围的窄线发射区云是一致的。我们还讨论了从黑洞尺度到pc尺度的磁场配置以及低极化的起源。
英文摘要：
We present Very Long Baseline Array polarimetric observations of the innermost jet of 3C$\sim$84 (NGC$\sim$1275) at 43$\sim$GHz. A significant polarized emission is detected at the hotspot of the innermost re-started jet, which is located $\sim$1 pc south from the radio core. While the previous report presented a hotspot at the southern end of the western limb, the hotspot location has been moved to the southern end of the eastern limb. Faraday rotation is detected within an entire bandwidth of the 43-GHz band. The measured rotation measure (RM) is at most (6.3$\pm$1.9)$\times10^{5}$$\sim$rad$\sim$m$^{-2}$ and might be slightly time variable on the timescale of a month by a factor of a few. Our measured RM and the RM previously reported by the CARMA and SMA observations cannot be consistently explained by the spherical accretion flow with a power-law profile. We propose that a clumpy/inhomogeneous ambient medium is responsible for the observed rotation measure. Using equipartition magnetic field, we derive the electron density of $2\times10^{4}$$\sim$cm$^{-3}$. Such an electron density is consistent with the cloud of narrow line emission region around the central engine. We also discuss the magnetic field configuration from black hole scale to pc scale and the origin of low polarization.
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