A Systematic Search for Stars in Almost-Dark Galaxies

星系是恒星、气体、尘埃和暗物质的集合，它们都是由引力聚集在一起的。近100年前，美国天文学家埃德温·哈勃首次指出，星系是由数十亿颗恒星组成的孤岛宇宙。研究人员试图了解星系是如何形成和随时间变化的。他们的目标是确定产生观测到的各种星系的恒星形成过程。研究人员选择了一组附近富含气体的星系作为特别研究对象。这些星系是用阿雷西博射电望远镜发现的。这些星系含有大量的中性氢（HI）气体，这是新一代恒星的原始成分。此外，参与该项目的研究生和本科生将在科学研究、技术和数学方法、图像处理和分析以及计算机编程方面获得专业发展和培训。ALFALFA调查是一项HI调查，旨在对当地宇宙中的中性氢气进行统计完整的普查。ALFALFA覆盖了7000平方度的天空，并记录了3万个物体。该项目旨在测量两种特定类型ALFALFA源的光学特性：超紧凑高速云（UCHVCs），这是中性氢气云，具有使其成为附近低质量星系的良好候选者的特性，以及“几乎黑暗”星系，这是HI源，具有更大范围的可能距离和质量。这两类天体在现有的星表中都没有明确的光学对应，因此我们的目标是检测和表征这些天体的光学发射，以便更好地了解它们的特性和演化状态。为了实现这一目标，研究者和她的学生将使用WIYN 3.5米望远镜和1度成像仪（ODI）获得并分析从ALFALFA中选择的uchvc和近暗星系的明确样本的深，宽视场光学成像。这些观测结果将用于研究UCHVC和近暗样本的特性，并解决有关含有中性气体的星系如何形成和演化的重要问题。这些问题包括：UCHVCs对“丢失卫星问题”有什么影响？uchvc中有多少可以探测到恒星群？在局部体积内星系的环境和位置与它们的属性（例如，存在或不存在正在进行的恒星形成，它们的演化阶段）之间是否存在相关性？近暗星系的本质是什么？它们的性质与光学目录中的“正常”星系有何不同？近暗天体揭示了恒星形成是如何发生在HI质量与光学光度体系的极端末端的星系中？UCHVCs样本中的物体也可以用来帮助描述重子塔利-费舍尔关系，直到非常低的星系质量（小于1000万太阳质量），并探测宇宙的化学演化。研究者对研究生和本科生的支持和指导以及对学生的研究培训做出了重大承诺。该研究员还将与印第安纳大学创新教学中心的顾问合作，修改一门大型的非专业天文学入门课程。研究人员将在课程中使用光学和射电望远镜获取的数据来激发学生的兴趣，帮助说明所教授的概念，并展示现代天文学研究如何完成的具体例子。最后，作为Maria Mitchell协会董事会的成员，她将致力于推进科学推广和教育。Maria Mitchell协会是一个非营利性的研究、教育和推广组织，旨在推广美国第一位女性专业天文学家的遗产。

Galaxies are collections of stars, gas, dust, and dark matter, all held together by gravity. It is nearly 100 years since American Astronomer Edwin Hubble first showed that galaxies are island universes, containing of billions of stars. The investigators seek to understand how galaxies form and change over time. Their goal is identifying the star formation processes that produced the wide variety of galaxies observed. The investigators have selected for special study a set of nearby, gas-rich, galaxies. These galaxies were found with the Arecibo radio telescope. These galaxies contain large amounts of neutral hydrogen (HI) gas, the raw ingredient of new generations of stars. Furthermore, graduate and undergraduate students who work on the project will receive professional development and training in scientific research, technical and mathematical methods, image processing and analysis, and computer programming.The ALFALFA survey is a HI survey aimed at constructing a statistically-complete census of neutral hydrogen gas in the local universe. ALFALFA covers 7000 square degrees of sky and has cataloged 30,000 objects. This project aims to measure the optical properties of two specific types of ALFALFA sources: Ultra-Compact High Velocity Clouds (UCHVCs), which are neutral hydrogen gas clouds with properties that make them good candidates for nearby low-mass galaxies, and "Almost-Dark" galaxies, which are HI sources with a wider range of possible distances and masses. Both classes of objects have no clear optical counterpart in existing catalogs, so the objective is to detect and characterize the optical emission from these objects in order to better understand their properties and evolutionary state. To accomplish this objective, the investigator and her students will obtain and analyze deep, wide-field, optical imaging with the WIYN 3.5-meter telescope and One Degree Imager (ODI) of a well-defined sample of UCHVCs and Almost-Dark galaxies chosen from ALFALFA. The observations will be used to investigate the properties of the UCHVC and Almost-Dark samples and address important questions about how galaxies with neutral gas form and evolve. These questions include: What implications do the UCHVCs have for the ``missing satellites problem''? What fraction of the UCHVCs have detectable stellar populations? Are there correlations between the galaxies' environments and locations within the Local Volume and their properties (e.g., the presence or absence of ongoing star formation, their evolutionary phase)? What is the nature of the Almost-Dark galaxies, and how do their properties differ from ``normal'' galaxies in optical catalogs? What do the Almost-Dark objects reveal about how star formation takes place in galaxies at the extreme end of the HI mass to optical luminosity regime? The objects in the UCHVCs sample can also be used to help characterize the Baryonic Tully-Fisher Relation down to very low galaxy masses (less than ten million solar masses) and to probe the chemical evolution of the Universe.The investigator has made major commitments to the support and mentoring of graduate and undergraduate students, and to the training of students in research. The investigator will also work with consultants at the Indiana University Center for Innovative Teaching and Learning to revise a large introductory astronomy course for non-majors. The investigator will use the data taken with optical and radio telescopes in a course to pique student's interest, help illustrate the concepts being taught, and show concrete examples of how modern research is done in astronomy. Finally, the investigator will work on advancing science outreach and education through her membership on the Board of Directors of the Maria Mitchell Association, a non-profit research, education, and outreach organization that promotes the legacy of America's first female professional astronomer.