Milliarcsecond Polarization Measurements of Compact Extragalactic Radio Sources

紧凑星系外射电源的毫角秒偏振测量厘米波长射电天文学用于在非常小的尺度上研究活动星系核（AGN）。这是通过甚长基线偏振法完成的，通过该方法，紧凑射电源的线性偏振结构可以在毫弧秒的角度尺度上确定，对应于活动星系核（AGN）距离上光年的物理尺度。这种高角度分辨率允许在中等时间尺度（一年或更短）上跟踪射流结构的变化，偏振法揭示了磁场的顺序和方向，并允许研究AGN中心周围的热粒子环境。通过观察两个或多个波长并使用法拉第效应，可以在AGN活动中心喷出的高度相对论性等离子体射流中传播激波的模型框架中绘制和解释AGN的发射线区域。最终目标是详细阐述驱动AGN的机制，目前认为AGN是对大质量黑洞的吸积。

AST 95-29228 PI: David Roberts Milliarcsecond Polarization Measurements of Compact Extragalactic Radio Sources Radio astronomy at centimeter wavelengths is used to study active galactic nuclei (AGN) on the very small scales. This is accomplished with Very Long Baseline Polarimetry, by which the linear polarization structure of compact radio sources may be determined on angular scales of milliarcseconds, corresponding to physical scales of light years at the distances of Active Galactic Nuclei (AGN). This high angular resolution allows changes in the structure of jets to be followed on moderate time scales (a year or less), and the polarimetry reveals the order and orientation of the magnetic field and allows study of the thermal particle environment around the heart of AGN. By observing at two or more wavelengths and using the Faraday effect, the emission line regions of AGN can be mapped out and interpreted in the framework of a model in which shock waves propagate in jets of highly relativistic plasma ejected from the active centers of AGN. The ultimate goal is to elaborate the mechanism that powers AGN, currently thought to be accretion onto massive black holes.