A Pioneering Test of Stellar Population Complexity Outside the Milky Way

研究人员将测试银河系化学成分的独特性。他们的目标是基于对银河系恒星的观测，了解其他星系是如何随时间变化的。对MW中单个恒星的观测表明，恒星的化学和运动是相关的。这些关系指导我们理解其他星系是如何随时间变化的，并在化学上丰富了宇宙。研究其他星系随时间的变化是极其困难的。该项目团队将率先采用新技术来测试这些模式是否出现在仙女座星系中，仙女座星系是最近的星系，与MW相似。这些测量将提供对该星系历史的深入了解，MW的独特性，以及这些系统在追踪大爆炸以来星系如何成长方面的有用性。为了分析现有的高分辨率，近红外（NIR）光谱跨越仙女座凸起和圆盘的很大一部分，项目团队将首先建立一个基于理论等时线和近40万颗恒星光谱观测的简单恒星人口（SSP）模型库。这个NIR库的公开发布将填补社区可用的SSP库套件的空白。项目团队将应用该库以两种方法对仙女座菌株的综合光谱进行建模，一种是使用多分量光谱拟合，另一种是使用机器学习与SSP模型作为训练集。两种方法的比较将用于评估银河系不同部分结果的一致性和稳健性。这个项目将限制仙女座内部区域重叠恒星群的存在，这些恒星群具有不同的动力学和化学性质，反映了它们不同的历史，这些信息以前只在MW中被测量过。通过揭示仙女座星系在这一重要方面与特大星系的相似之处，该项目将阐明我们的特大星系高分辨率图像在多大程度上可以应用于解释其他星系中未解析的星光。更一般地说，这些结果将检验关于凸起和内盘演化的理论，以及这种演化如何反映在构成恒星群中。该项目还支持向项目团队所在的两个重要群体——犹他州的难民社区和犹他州国家公园的游客——推广科学素养。该团队将开发以天文学为主题的研讨会，作为课后项目的一部分，帮助来自难民家庭的初高中学生融入美国课堂并获得社会支持。这些研讨会将促进对科学的积极认识，并向因家庭历史而在教育上面临独特挑战的学生传授批判性思维、沟通和计算技能。该项目还包括一项影响深远的外展实习计划的扩展，为布莱斯峡谷国家公园的约1.8万名游客提供天文学教育。这两项努力将通过来自难民社区的学生访问布莱斯峡谷，在美国最黑暗的天空下进行身临其境的户外体验而联系起来。该奖项反映了美国国家科学基金会的法定使命，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。

The investigator will test the uniqueness of the Milky Way Galaxy's chemical composition. Their goal is understanding how other galaxies change with time, based on observations of stars in the Milky Way (MW). Observations of individual stars in the MW show that the chemistry and the motions of stars are related. These relationships have guided our understanding of how other galaxies change over time and chemically enrich the Universe. Studying the changes in other galaxies over time is extremely difficult. The project team will pioneer new techniques for testing if these patterns occur in the Andromeda Galaxy, the nearest galaxy that is similar to the MW. These measurements will provide insight into that galaxy's history, the uniqueness of the MW, and the usefulness of these systems for tracing how galaxies have grown since the Big Bang. To analyze existing high-resolution, near-infrared (NIR) spectra spanning a large fraction of Andromeda's bulge and disk, the project team will first construct a library of Simple Stellar Population (SSP) models based on theoretical isochrones and nearly 400,000 stellar spectra observations. The public release of this NIR library will fill a gap in the suite of SSP libraries available to the community.The project team will apply this library in two approaches to modeling the Andromeda integrated spectra, one using multi-component spectral fitting and one using machine learning with the SSP models as a training set. The comparison of the two approaches will be used to evaluate the consistency and robustness of the results in different parts of the galaxy. This program will constrain the presence of overlapping stellar populations in the inner regions of Andromeda with distinct dynamical and chemical properties that reflect their diverse histories, information that previously has been measured only in the MW. By revealing how similar Andromeda is to the MW in this important regard, this project will clarify to what extent our high-resolution picture of the MW can be applied to interpreting the unresolved starlight in other galaxies. More generally, these results will test theories of bulge and inner disk evolution and how that evolution is reflected in the constituent stellar populations.This program also supports efforts to promote scientific literacy to two important groups local to the project team: Utah's refugee community and visitors to Utah's national parks. The team will develop astronomy-themed workshops as part of an after-school program that helps middle- and high-school students from refugee families integrate into American classrooms and find social support. These workshops will promote positive perceptions of science and teach critical thinking, communication, and computational skills to students who face unique challenges to their education because of their family histories. The project also includes an extension of a high-impact outreach internship program to bring astronomy education to about 18,000 visitors at Bryce Canyon National Park. These two efforts will be linked by a visit of students from the refugee community to Bryce Canyon for an immersive outdoor experience under some of the US's darkest skies.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.