The Role of Cosmic Magnetic Fields in Galaxy Evolution

宇宙磁场在星系演化中的作用

• 批准号: RGPIN-2014-04042
• 负责人: Stil, Jeroen
• 金额: $ 1.82万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=566259
• 关键词: Role; Cosmic; Magnetic; Fields; Galaxy

The Role of Magnetic Fields in Galaxy Formation Earth's magnetic field protects our atmosphere from the onslaught of the solar wind: a stream of plasma flowing from the Sun through the Solar System. A disturbance in the Sun's magnetic field can trigger a massive ejection of matter into space that can cause power outages and disruption of GPS equipment and satellite communication when it interacts with the Earth's magnetic field. Recently, NASA's Voyager 1 space probe recorded a sudden change in magnetic field strength, but not direction, as it presumably entered interstellar space. Magnetic fields pervade the universe. In many astrophysical situations from small to very large, magnetic fields play a decisive part in the motion of matter in the cosmos. In return the structure of cosmic magnetic fields is intimately related to the motion of matter. Understanding magnetic fields is necessary to understand the formation of structure, and its subsequent evolution. In this proposal I outline a research program that investigates the physics of magnetic fields in relation to the formation and evolution of galaxies. This includes galaxy assembly by accretion of matter, but also the interaction between magnetic fields and matter inside galaxies, and activity in the centre of galaxies (Active Galactic Nucleus or AGN) that ejects vast amounts of energy in the form of beams of matter into intergalactic space. For the moment, we know very little with confidence about magnetic fields in galaxies. This is in part due to limitations in the predictive nature of dynamo theory that describes how large-scale magnetic fields can be amplified and sustained from motions in an astrophysical plasma. In part, our lack of understanding of cosmic magnetic fields is due to limitations in our ability to derive quantitative information from observations. The latter will make significant steps forward in the next decade because of recent developments in receiver technology, and the design of a new international facility for radio astronomy called the Square Kilometre Array (SKA). One of five key science goals for the SKA is to study the origin and evolution of cosmic magnetism, and another includes galaxy evolution and cosmology. For normal galaxies, I investigate the relation of the magnetic field to global properties such as the rate of star formation and dynamics of a galaxy. To this end, I lead surveys with the Effelsberg radio telescope and the Expanded Very Large Array (EVLA). On much smaller scales in our own Milky Way galaxy, I investigate the connection between the gas and the small-scale magnetic field. I lead the polarization side of a survey of part of the disk of the Milky Way (THOR), and an early science project of the GALFACTS survey with the Arecibo 300-m radio telescope. Through collaboration on deep surveys of small areas of the sky, we investigate the properties of distant galaxies and AGN-powered radio sources. The magnetic field properties of radio galaxies are also the subject of a statistical investigation using a technique called stacking, and another early science project with the GALFACTS survey. This work includes both observations with state of the art facilities and modeling of radio emission and magnetic fields. In support of development of future sky surveys with SKA and its path finders, I am also investigating new applications to extract information from broad-band observations of the polarization of radio waves, the principal source of information about cosmic magnetic fields. This will lead to a deeper understanding of the origin of magnetic fields in the cosmos, and their role in the formation of structure in the universe.

磁场在星系形成中的作用地球磁场保护我们的大气层免受太阳风的攻击：太阳风是从太阳流经太阳系的等离子体流。太阳磁场的扰动会引发大量物质喷射到太空中，当它与地球磁场相互作用时，可能会导致停电、GPS 设备和卫星通信中断。最近，美国宇航局航海者一号太空探测器记录到磁场强度的突然变化，但没有记录到方向的变化，因为它可能进入了星际空间。磁场遍布宇宙。在许多从小到大的天体物理情况下，磁场在宇宙中物质的运动中起着决定性的作用。反过来，宇宙磁场的结构与物质的运动密切相关。了解磁场对于了解结构的形成及其随后的演化是必要的。在这个提案中，我概述了一个研究项目，该项目研究与星系形成和演化相关的磁场物理学。这包括通过物质吸积而形成的星系组装，还包括磁场与星系内部物质之间的相互作用，以及星系中心（活动星系核或AGN）的活动，这些活动以物质束的形式将大量能量喷射到星系间空间。目前，我们对星系中的磁场知之甚少。这部分是由于发电机理论的预测性质的局限性，该理论描述了如何通过天体物理等离子体的运动来放大和维持大规模磁场。我们对宇宙磁场缺乏了解的部分原因是我们从观测中获取定量信息的能力有限。由于接收器技术的最新发展以及称为平方公里阵列（SKA）的新国际射电天文学设施的设计，后者将在未来十年中取得重大进展。 SKA 的五个关键科学目标之一是研究宇宙磁力的起源和演化，另一个包括星系演化和宇宙学。对于正常星系，我研究磁场与全局属性（例如恒星形成速率和星系动力学）的关系。为此，我使用埃菲尔斯伯格射电望远镜和扩展甚大阵列 (EVLA) 进行了调查。在我们银河系的更小尺度上，我研究了气体和小尺度磁场之间的联系。我领导了部分银河系盘面巡天 (THOR) 的偏振侧项目，以及使用阿雷西博 300 米射电望远镜进行的 GALFACTS 巡天早期科学项目。通过合作对天空小区域进行深度调查，我们研究了遥远星系和活动星系核供电的无线电源的特性。射电星系的磁场特性也是使用堆叠技术进行统计调查的主题，也是 GALFACTS 调查的另一个早期科学项目的主题。这项工作包括使用最先进的设施进行观测以及无线电发射和磁场的建模。为了支持 SKA 及其探路者未来天空勘测的发展，我还在研究新的应用程序，以从无线电波偏振的宽带观测中提取信息，这是宇宙磁场信息的主要来源。这将导致人们更深入地了解宇宙磁场的起源及其在宇宙结构形成中的作用。