Galaxy Evolution and Environment -- Disk-Halo Outflows, Feedback and Magnetic Fields

星系演化与环境——盘晕流出、反馈和磁场

• 批准号: RGPIN-2016-03617
• 负责人: Irwin, Judith
• 金额: $ 1.6万
• 依托单位: Queen's University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=614499
• 关键词: Galaxy; Evolution; Environment; Disk; Halo

My program involves a study of outflows from spiral galaxies and their effect on galaxy formation and evolution. Current models require strong outflows (called 'feedback') in order to form the galaxies that we see today. But the details of feedback mechanisms are not well known and current computer simulations must include assumptions about feedback which are reasonable, but not verified through observation. Fortunately, we now know that nearby fully formed galaxies also experience outflows that are lower in power yet similar in nature to those that occurred at a time when galaxies first formed. Nearby galaxies, not only are fully formed versions of their infant counterparts, but also represent local laboratories within which outflows can be studied in great detail. With careful scrutiny, we can identify and quantify the important physics, dynamics, causes and effects of this important activity. In this Discovery Grant (DG) cycle, I will primarily focus on radio continuum emission from the interaction between cosmic rays and magnetic fields.The consequences of outflows are substantial. Significant gas is expelled from the disk leading to modifications in the galaxy's evolution (e.g. adjusted star formation rates, re-distribution of chemical elements, altered magnetic field structures). There are important implications both locally (such as around our own Sun) and globally across a galaxy. For example, our Sun exists in a 'local hot bubble' which is believed to have been excavated by previous supernova activity. Could this have affected the formation and evolution of our Sun and, by implication, the Earth itself? Indeed the Galactic `habitable zone' will certainly be affected by outflows. My first goal is to complete the full data release of CHANG-ES (Continuum Halos in Nearby Galaxies -- an EVLA Survey), an international consortium of which I am principal investigator. We have used the EVLA (Expanded Very Large Array) radio telescope, whose correlator was built in Canada, to observe 35 edge-on galaxies in a variety of telescope configurations, at an opportunistic time prior to the future Square Kilometre Array. Our 405 hours of EVLA data constitute 175 data sets which include, for the first time, information on the magnetic field direction in edge-on galaxies. Green Bank Telescope time has also been awarded.Canada, via CHANG-ES, has become a center of excellence in high quality training for processing interferometric data sets and dealing with `big data'. Our first legacy-value public data release occurred in August/2015 and there will be two more over the time period of this DG. Our own consortium is making new discoveries from these data (see text). With the public data release, other scientists will also benefit from the results, leveraging our own work. Our group's focus has shifted more and more towards the science, and we anticipate many more answers (and surprises) in the future.

我的项目包括研究螺旋星系的外流及其对星系形成和演化的影响。为了形成我们今天看到的星系，目前的模型需要强大的流出（称为“反馈”）。但反馈机制的细节尚不清楚，目前的计算机模拟必须包括有关反馈的假设，这些假设是合理的，但尚未通过观察得到验证。幸运的是，我们现在知道，附近完全形成的星系也会经历流出，这些流出的能量较低，但性质与星系刚形成时发生的流出相似。附近的星系，不仅是它们的婴儿星系的完全形成的版本，而且还代表了当地的实验室，在那里可以对流出物进行详细的研究。经过仔细审查，我们可以确定和量化这一重要活动的重要物理、动力学、原因和影响。在这个发现基金（DG）周期中，我将主要关注宇宙射线和磁场之间相互作用产生的射电连续体发射。资本外流的后果是巨大的。大量气体从圆盘中排出，导致星系演化的改变（例如，调整恒星形成率，化学元素的重新分布，改变磁场结构）。这对局部（比如我们的太阳周围）和整个星系都有重要的影响。例如，我们的太阳存在于一个“局部热泡”中，据信这是由以前的超新星活动挖掘出来的。这是否会影响太阳的形成和演化，进而影响地球本身呢？事实上，银河系的“宜居带”肯定会受到外流的影响。我的第一个目标是完成CHANG-ES（附近星系连续光晕- EVLA调查）的全部数据发布，这是一个由我担任首席研究员的国际联盟。我们已经使用EVLA（扩展超大阵列）射电望远镜，其相关器是在加拿大建造的，在未来的平方公里阵列之前的一个机会时间，在各种望远镜配置中观察35个边缘星系。我们405小时的EVLA数据构成了175个数据集，其中首次包含了关于边缘星系磁场方向的信息。绿岸望远镜时间也被授予。通过CHANG-ES，加拿大已成为处理干涉测量数据集和处理“大数据”的高质量培训中心。我们的第一次遗产价值公开数据发布于2015年8月，在此DG期间还将发布两次。我们自己的联盟正在从这些数据中获得新的发现（见原文）。随着公开数据的发布，其他科学家也将从结果中受益，利用我们自己的工作。我们小组的重点已经越来越多地转向科学，我们预计未来会有更多的答案（和惊喜）。