Cosmic magnetism

磁力是自然界的基本力量之一。众所周知，星系中存在磁场，从孕育超大质量黑洞的高能原子核，到星系盘中恒星之间的扩散介质。众所周知，在控制许多驱动星系演化的现象方面，从恒星形成、结构形成、大规模动力学到高能粒子的限制和加速，磁力都是至关重要的。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。射电发射极化是研究宇宙磁场的关键探测器之一。宇宙磁学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。本提案中描述的研究将通过使用世界上最强大的射电望远镜进行大型观测项目，在空间和频率上绘制来自天空的极化发射图，从而大大提高我们对宇宙磁场起源、演化和作用的理解。GALFACTS使用阿雷西博望远镜上的多馈源喇叭阵列，对40%的天空进行成像，其灵敏度是以往任何偏振调查的五倍，并具有频率依赖的全光谱信息。该项目将测量超过10万个射电源的偏振特性，并绘制出银河系中磁场与星际介质相互作用产生的漫射极化发射图。EVLA深偏振场将测量从星系盘到高红移的微弱偏振信号，追踪宇宙年龄相当一部分的星系场的演化。这些项目结合了先进观测和数据处理技术的开发、前沿科学、与全球领先研究人员网络的合作以及与主要天文台和行业的伙伴关系，为培养能够在先进技术和世界一流科学的界面工作的年轻科学家提供了肥沃的环境。

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.