Collaborative Research: Non-thermal Radio Halos of Spiral Galaxies as Clues to Galaxy Evolution

要了解像太阳这样的恒星和像地球这样的行星是如何形成的，我们必须了解像银河系这样的星系是如何形成和演化的。这个项目试图了解星际气体和高能粒子是如何从星系盘中喷射出来的，而星系盘是发现大多数气体和恒星的地方，并与星系晕相互作用。这个循环过程对于理解星系中恒星形成的过程以及星系形成时的增长速度非常重要。这项研究利用了由美国国家科学基金会资助的卡尔·g·扬斯基甚大阵列（VLA）和绿岸望远镜（GBT）的无线电图像，阿帕奇点3.5米望远镜的光学数据，以及存档的红外数据。该项目将为西班牙裔服务机构的两名博士生提供撰写论文的机会，而这些pi还将为美国国家射电天文台为小型学院的教职员工开展的一项培训计划做出贡献。星系的成长和演化既依赖于从星系环境中获得的气体，也依赖于从星系盘中流出的能量。需要了解这些过程的详细物理原理，而附近的边缘星系是最好的对象，在那里可以干净地分离盘和晕的成分。该项目利用了一项名为CHANG-ES（附近星系的连续光晕：EVLA调查）的大型新调查，该调查是对边缘星系的射电连续发射进行的。第一个目标是利用VLA和GBT制作的无线电地图，通过评估星系晕中非热气体压力梯度的作用，进一步了解盘晕流动的动力学。第二个目标是确定宇宙射线（CR）注入和传播到星系晕的位置。为此，将利用CHANG-ES地图结合红外数据和H-alpha图像对热射电发射和非热射电发射进行稳健分离，绘制非热光谱指数的空间变化。第三个科学目标是检验CR流出与热气体盘晕循环之间的联系，以及这种关系是否取决于恒星形成速率等因素。

To understand how stars like the Sun and planets like Earth came to be, we must understand how galaxies, such as our Milky Way, form and evolve. This project is an attempt to understand how interstellar gas and energetic particles are ejected from galaxy disks, where most of the gas and stars are found, and interact with the galaxy halo. This cyclical process is important for understanding how star formation proceeds in galaxies, and the rate at which galaxies grew when they were forming. The study makes use of radio images from the NSF-funded Karl G. Jansky Very Large Array (VLA) and the Green Bank Telescope (GBT), optical data from the Apache Point 3.5-meter telescope, as well as archival infrared data. The project will provide opportunities for two PhD student theses at Hispanic Serving Institutions, and the PIs will also contribute to a training program run by the National Radio Astronomy Observatory for faculty at small colleges.Galaxy growth and evolution depend on both the acquisition of gas from the galaxy environment and energetic outflows from disks. The detailed physics of these processes needs to be understood, and nearby edge-on galaxies are the best objects where it is possible to cleanly separate disk and halo components. The project leverages a major new survey of radio continuum emission from edge-on galaxies called CHANG-ES (Continuum Halos in Nearby Galaxies: an EVLA Survey). The first goal is to further our understanding of the dynamics of disk-halo flows by assessing the role of non-thermal gas pressure gradients in galaxy halos, using radio maps made from the VLA and GBT. The second goal focuses on identifying sites of cosmic ray (CR) injection and propagation into galaxy halos. For this, the spatial variation of the non-thermal spectral index will be mapped, after robustly separating thermal and non-thermal radio emission using CHANG-ES maps in conjunction with infrared data and H-alpha images. The third science goal is to examine the connection between CR outflows and disk-halo cycling of thermal gas, and whether this relation depends on factors such as star formation rate.