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.

我的项目涉及螺旋星系的流出及其对星系形成和演化的影响的研究。当前的模型需要强烈的流出（称为“反馈”）才能形成我们今天看到的星系。但反馈机制的细节尚不清楚，当前的计算机模拟必须包括合理的反馈假设，但未经观察验证。幸运的是，我们现在知道附近完全形成的星系也会经历功率较低但性质与星系首次形成时发生的流出相似的流出。附近的星系不仅是其婴儿星系的完全形成版本，而且还代表了可以对流出物进行详细研究的当地实验室。通过仔细审查，我们可以识别并量化这一重要活动的重要物理、动力学、原因和影响。在本次发现补助金 (DG) 周期中，我将主要关注宇宙射线与磁场之间相互作用产生的无线电连续发射。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（例如调整恒星形成速率、化学元素重新分布、改变磁场结构）。这对于局部（例如在我们自己的太阳周围）和整个星系的全球都有重要影响。例如，我们的太阳存在于一个“局部热气泡”中，据信该气泡是由之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，并暗示地球本身的形成和演化？事实上，银河系“宜居区”肯定会受到外流的影响。我的第一个目标是完成 CHANG-ES（邻近星系的连续光晕——一项 EVLA 巡天）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。我们使用了 EVLA（扩展甚大阵列）射电望远镜（其相关器是在加拿大建造的），在未来平方公里阵列之前的机会时期以各种望远镜配置观测了 35 个边缘星系。我们 405 小时的 EVLA 数据由 175 个数据集组成，其中首次包含了边缘星系磁场方向的信息。 Green Bank Telescope时间也被授予。加拿大通过CHANG-ES，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。我们的第一个遗留价值公共数据发布于 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（见正文）。随着公开数据的发布，其他科学家也将利用我们自己的工作从结果中受益。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答案（和惊喜）。