Direct Mapping of Radiative Feedback in Galaxies

来自大质量恒星的电离辐射是单个星系和宇宙本身能量收支的主要组成部分。了解这些光子的命运是理解星系和宇宙演化的基础。来自恒星爆发星系的电离莱曼连续辐射的逃逸分数一般只有几个百分点，而且看起来是“被困住的”。相比之下，普通恒星形成星系中离散的HII区域似乎有大量具有长路径的电离光子的泄漏。为了提高我们对这些高能光子命运的理解，Oey博士和她的团队研究了不同尺度现象中的这种反差行为。最终，这将导致对具有不同恒星形成性质的不同类型星系产生的紫外场的观测测试描述。该团队使用现代宽视场、窄带成像技术来直接识别光学薄与光学厚的HII区域，并进行电离参数映射。他们计划对大小麦哲伦星云的星云光学厚度和较冷的星际相之间的关系进行定量的参数化，并将直接测量附近M31和M33星系的星云群的光学厚度，再次将这些光学厚度与星际介质环境联系起来。这项技术也被应用于附近的星暴星系，以评估电离辐射的逃逸和相关的电离形态。这些结果应该会对天体物理界产生广泛的影响，因为莱曼连续辐射的命运是宇宙演化中最重要的悬而未决的问题之一。同样，这些结果应该有助于理解恒星形成星系中弥漫的、温暖的电离介质的电离。该项目的影响范围从单个恒星到宇宙本身。这项工作直接建立在Oey博士关于大质量恒星反馈的综合计划上。该项目将使用马里兰州-麦哲伦可调窄带过滤器，该过滤器是在NSF的支持下建造的。一名研究生将接受使用可调滤波装置的培训，目前正在使用现有的和计划中的新一代望远镜。PI参与了几项外联活动，包括与历史悠久的密歇根大学底特律天文台的合作，后者正开始向本科生和公众开放其设施。PI和她的团队继续参与密歇根大学自然历史展览博物馆以及最近的密歇根大学博物馆研究计划，将促进博物馆环境中的科学教育。

The ionizing radiation from massive stars is a major component of the energy budget of individual galaxies and of the cosmos itself. Knowing about the fate of these photons is fundamental to understand both galaxy and cosmic evolution. The escape fraction of Ionizing Lyman continuum radiation from starburst galaxies generally is only a few percent, and appears to be "trapped". In contrast, discrete HII regions in ordinary star-forming galaxies seem to have substantial leakage of ionizing photons having long path lengths. Dr. Oey and her team investigate this contrasting behavior in different scale phenomena in order to improve our understanding of the fate of these energetic photons. Ultimately this can lead to an observationally tested description of the ultra-violet field emerging from different types of galaxies with different star-formation properties.The team uses modern wide-field, narrow-band imaging technology to directly identify optically thin versus optically thick HII regions and to do ionization-parameter mapping. They plan to quantitatively parameterize the relation between nebular optical depth and cooler interstellar phases for the large and small Magellanic Clouds, and will directly measure optical depths for the nebular population of the nearby galaxies M31 and M33, again relating these to the interstellar medium environment.The technique is also applied to nearby starburst galaxies to evaluate the escape of ionizing radiation and related ionization morphology. These results should have broad impact in the astrophysical community, since the fate of Lyman continuum radiation is one of the most important outstanding issues in cosmic evolution. Likewise, the results should contribute to the understanding of the ionization of the diffuse, warm ionized medium in star-forming galaxies. The project has impact on scales ranging from individual stars to the cosmos itself. The work builds directly on the Dr. Oey's comprehensive program on feedback from massive stars.This project will use the Maryland-Magellan Tunable Narrow Band Filter, which was built with NSF support. A graduate student will be trained in the use of tunable filter devices, which are now being commissioned on existing and planned new-generation telescopes. The PI is involved in several outreach activities, including a partnership with the historic University of Michigan Detroit Observatory, which is starting to open its facilities to undergraduate students and the public. The continued involvement by the PI and her team with the University of Michigan Exhibit Museum of Natural History and more recently, the University of Michigan Museum Studies Program will advance science education in the museum environment.