A Systematic Search for Stars in Almost-Dark Galaxies

星系团是恒星、气体、尘埃和暗物质的集合，它们都被引力聚集在一起。 自从美国天文学家埃德温·哈勃首次证明星系是岛屿宇宙，包含数十亿颗恒星以来，已经过去了近100年。 研究人员试图了解星系是如何随着时间的推移而形成和变化的。他们的目标是确定产生观测到的各种星系的星星形成过程。 研究人员选择了一组附近的富含气体的星系进行特殊研究。 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材料。 此外，参与该项目的研究生和本科生将获得科学研究、技术和数学方法、图像处理和分析以及计算机编程等方面的专业发展和培训。ALCHARFA调查是一项HI调查，旨在对本地宇宙中的中性氢气进行全面的普查。ALGOFA覆盖了7000平方度的天空，并编目了30，000个物体。 该项目旨在测量两种特定类型的ALCHFA源的光学特性：超紧凑高速云（UCHVC），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，这是具有更大范围的可能距离和质量的HI源。 这两类天体在现有的星表中没有明确的光学对应物，因此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性质和演化状态。为了实现这一目标，研究人员和她的学生将获得和分析深，宽视场，光学成像与WIYN 3.5米望远镜和一度成像仪（ODI）的UCHVC和Almost-Dark星系的定义明确的样本选择从ALOCHFA。 这些观测结果将用于研究UCHVC和几乎黑暗样本的性质，并解决有关中性气体星系如何形成和演化的重要问题。这些问题包括：UCHVC对"失踪卫星问题“有什么影响？ UCHVCs中有多少部分具有可探测的恒星群？ 星系的环境和在本地体积内的位置与它们的属性（例如，是否存在正在进行的星星形成，它们的进化阶段）？ 几乎暗星系的性质是什么？它们的性质与光学目录中的“正常”星系有何不同？ 几乎暗天体揭示了在HI质量与光学光度制度极端的星系中星星是如何形成的？ UCHVC样品中的物体也可以用来帮助描述重子塔利-费舍尔关系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。研究人员已经做出了重大承诺，支持和指导研究生和本科生，并对学生进行研究培训。 研究人员还将与印第安纳州大学创新教学中心的顾问合作，为非专业学生修改一门大型天文学入门课程。 研究人员将在课程中使用光学和射电望远镜拍摄的数据来激发学生的兴趣，帮助说明正在教授的概念，并展示现代天文学研究如何完成的具体例子。 最后，研究人员将通过她在玛丽亚·米切尔协会董事会的成员资格，致力于推进科学推广和教育，该协会是一个非营利性的研究，教育和推广组织，旨在促进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.