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: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=708818
• 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.

我的计划涉及研究螺旋星系的外流及其对星系形成和演化的影响。目前的模型需要强烈的外流(称为‘反馈’)，才能形成我们今天所看到的星系。但反馈机制的细节还不是很清楚，目前的计算机模拟必须包括关于反馈的合理假设，但没有通过观察进行验证。幸运的是，我们现在知道，附近完全形成的星系也经历了能量较低但性质类似于星系刚形成时发生的流出。附近的星系，不仅是其幼年星系的完全成型版本，而且还代表着地方实验室，在其中可以非常详细地研究外流。通过仔细的审查，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。在这个探索奖助金(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谱发射。 资本外流的后果是巨大的。大量气体从盘中排出，导致星系演化的改变(例如，调整后的恒星形成速率、化学元素的重新分布、磁场结构的改变)。这对银河系的局部(例如围绕我们的太阳)和全球都有重要的影响。例如，我们的太阳存在于一个“局部热泡”中，据信是由先前的超新星活动挖掘出来的。这是否影响了太阳的形成和演化，也就是地球本身？的确，银河系的“宜居区”肯定会受到外流的影响。 我的第一个目标是完成CHANGES(邻近星系中的连续晕--EVLA调查)的完整数据发布，这是一个国际联盟，我是该联盟的首席研究员。我们已经使用了EVLA(扩展甚大阵列)射电望远镜，其相关器建在加拿大，在未来的平方公里阵列之前的一个机会时间，观测了各种望远镜配置的35个边缘星系。我们405小时的EVLA数据组成了175个数据集，其中第一次包括了边缘星系中磁场方向的信息。绿岸望远镜时间也已获奖。 通过CHANGES，加拿大已成为处理干涉数据集和处理“大数据”的高质量培训的卓越中心。我们的第一次遗产价值公开数据发布于2015年8月/日，在本DG的时间段内还将发布两次。我们自己的财团正在根据这些数据做出新的发现(见正文)。随着公开数据的发布，其他科学家也将受益于这些结果，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)。