RUI: How Porous is the Warm Ionized ISM? Drilling in with Pulsars

我们自己的银河系由恒星组成，但恒星之间也有大量的物质。天文学家称这种物质为星际介质或简称ISM。ISM的大部分由质子数与电子数相同的中性原子组成。然而，大约3%的气体有一个或多个电子被附近恒星的光子撞飞。研究人员试图了解这种电离气体的渗透性有多大。 换句话说，它就像一个厚厚的浓雾，在所有方向上都是相同的密度。 或者，他们的测量结果可能会显示气体更像是一团蓬松的云，在夏天的一天漂浮在头顶上。 这些问题对于理解银河系的整个恒星形成生态系统非常重要。 该项目还将支持本科生的研究人员，无论是在他们的学年和夏季。他们将学习适用于国家科学和技术工作的研究，组织和沟通技能。项目负责人将积极努力招募不同的学生群体来参与这个项目。 研究人员试图提高对银河系中温暖的电离气体的理解。简称WIM，是银河系压力支持的重要组成部分。脉冲星是旋转的中子星，是WIM的优秀探测器，因为它们产生的无线电波在穿过WIM时被延迟和散射。 当无线电脉冲通过离散的电离结构（透镜状）时，这些原本不可见的特征就会显现出来。 研究人员和学生将在无线电波中寻找微妙但易于检测的特征，以确定散射无线电波的材料的位置和物理条件。美国主要的射电望远镜，如阿雷西博天文台和绿色银行望远镜将用于这项工作。其中一部分工作将使用荷兰的LOFAR望远镜进行，该望远镜的无线电频率比其他两台望远镜低得多。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Our own Milky Way galaxy consists of stars but also a substantial amount of material in between the stars. Astronomers call this material the interstellar medium or ISM for short. Much of the ISM consists of neutral atoms that have the same number of protons as electrons. However, about 3% of the gas has had one or more electrons knocked free by photons from nearby stars. The investigators seek to know how porous this ionized gas is. In other words, is it like a thick, dense fog and the same density in all directions. Alternatively, their measurements may show the gas is more like group of fluffy clouds drifting overhead on a summer’s day. These questions are important for understanding the entire star-forming ecosystem of the Milky Way. This project will also support undergraduate student researchers, both during their academic year and during the summer. They will learn research, organizational, and communication skills applicable the national science and technology effort. The project leader will actively work to recruit a diverse group of students to work on this project. The investigator seeks to improve understanding of the warm ionized gas in the Milky Way. Referred to as the WIM, it is an important part of the pressure support of the Milky Way. Pulsars, which are rotating neutron stars, are excellent probes of the WIM since the radio waves they generate are delayed and scattered by passage through the WIM. When the radio pulses pass through discrete ionized structures (lens-like in character), these otherwise invisible features are revealed. The investigator and students will search for subtle, but easy-to-detect, features in the radio waves to determine the location and physical conditions of the material that scatters the radio waves. Major US radio telescopes such as the Arecibo Observatory and the Green Bank Telescope will be used for this work. One portion of the work will be pursued using a telescope in the Netherlands called LOFAR, which observes at much lower radio frequency than the two other telescopes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.