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(MW)恒星的观测，了解其他星系如何随时间变化。对MW中的单个恒星的观测表明，化学和恒星的运动是相关的。这些关系指导了我们对其他星系如何随时间变化并在化学上丰富宇宙的理解。研究其他星系随时间的变化是极其困难的。该项目团队将率先开发新的技术来测试这些模式是否出现在仙女座星系中，仙女座星系是距离最近的星系，与微波辐射相似。这些测量将提供对该星系的历史、MW的独特性的洞察，以及这些系统在追踪星系自大爆炸以来如何增长的有用之处。为了分析现有的高分辨率近红外(NIR)光谱，跨越仙女座菌株的凸起和圆盘的很大一部分，项目组将首先基于理论等时线和近40万颗恒星光谱观测建立一个简单恒星群(SSP)模型库。这个近红外库的公开发布将填补社区可用的SSP库套件的空白。项目团队将以两种方法应用该库来模拟仙女座菌株的综合光谱，一种是使用多组分光谱拟合，另一种是使用机器学习以SSP模型作为训练集。这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。该计划将限制仙女座内部区域重叠恒星群的存在，这些重叠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，这些信息以前只以MW为单位进行测量。通过揭示仙女座在这一重要方面与微波的相似之处，这个项目将阐明我们的微波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分解的星光。更广泛地说，这些结果将测试凸起和内盘演化理论，以及这种演化如何反映在组成恒星的人口中。该计划还支持向项目团队当地的两个重要群体促进科学素养的努力：犹他州的难民社区和犹他州国家公园的游客。该团队将开发以天文为主题的研讨会，作为一个课外项目的一部分，该项目帮助来自难民家庭的初中生和高中生融入美国课堂，寻找社会支持。这些工作坊将促进对科学的积极看法，并向因家族史而面临独特教育挑战的学生传授批判性思维、沟通和计算技能。该项目还包括一个影响力很大的外展实习项目的延伸，在布莱斯峡谷国家公园为大约1.8万名游客带来天文教育。这两项努力将由难民社区的学生访问布莱斯峡谷，在美国一些最黑暗的天空下进行身临其境的户外体验而联系在一起。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.