Cosmic magnetism

磁力是自然界的基本力量之一。众所周知，星系中存在着磁场，从蕴藏着超大质量黑洞的高能核，到盘中恒星之间的扩散介质。众所周知，磁力在控制许多推动星系演化的现象方面至关重要，这些现象包括恒星形成、结构形成、大范围动力学以及高能粒子的限制和加速。尽管它们在宇宙中无处不在，也很重要，但人们对宇宙磁性的起源和演化知之甚少。射电辐射的偏振是研究宇宙磁场的关键探测器之一。宇宙磁性已被确定为下一代国际射电天文设施的关键科学目标之一，这些设施目前正在建设或计划中，如EVLA、澳大利亚SKA探路者和SKA。这项建议中描述的研究将通过使用世界上最强大的射电望远镜开展大型观测项目，绘制出来自天空的极化辐射在空间和频率上的地图，从而极大地促进我们对宇宙磁场的起源、演化和作用的理解。GALFACTS使用阿雷西博望远镜上的多馈喇叭阵列对40%的天空进行成像，其灵敏度是之前任何一次偏振测量的五倍，并具有与频率相关的全部光谱信息。该项目将测量超过1,000,000个射电源的偏振特性，并绘制我们银河系中磁场与星际介质相互作用产生的漫射极化辐射图。EVLA深极化场将测量从星系圆盘到高红移的微弱极化信号，追踪星系中场在宇宙年龄的很大一部分时间内的演变。这些项目结合了先进观测和数据处理技术的开发、尖端科学、与全球顶尖研究人员网络的合作，以及与主要天文台和工业肥沃环境的伙伴关系，以培养能够在先进技术和世界级科学的交汇处工作的年轻科学家。

Magnetism is one of the fundamental forces of nature. Magnetic fields are known to exist in galaxies, from the energetic nuclei that harbour super massive black holes, to the diffuse medium between the stars in the disks. Magnetic forces are known to be critically important in governing many of the phenomena that drive the evolution of galaxies, from star formation, structure formation, large-scale dynamics, and confinement and acceleration of high-energy particles. Despite their ubiquity and importance in the Universe, very little is known about the origin and evolution of cosmic magnetism. Polarization of radio emission is one of the key probes of cosmic magnetic fields. Cosmic magnetism has been identified as one of the key science goals of next generational international radio astronomy facilities that are currently under construction or planned, such as the EVLA, the Australia SKA Pathfinder and the SKA. The research described in this proposal will significantly advance our understanding of the origin, evolution and role of cosmic magnetic fields by using the world's most powerful radio telescopes to carry out large observing projects that map the polarized emission from the sky in both space and frequency. GALFACTS uses the multiple-feed horn array on the Arecibo telescope to image 40% of the sky to sensitivity five times deeper than the any previous polarization survey and with full spectral information of frequency dependence. This project will measure the polarization properties of over 1,00,000 radio sources and map the diffuse polarized emission from the interaction of magnetic fields with the interstellar medium in our Galaxy. The EVLA Deep Polarization Field will measure the faint polarized signals from disks of galaxies out to high redshifts, tracing the evolution of fields in galaxies over a significant fraction of the age of the universes. These projects combine development of advanced techniques for observing and data processing, cutting edge science, collaborations with a global network of leading researchers, and partnership with major observatories and industry - fertile environment to train young scientists who can work at the interface of advanced technologies and world-class science.