Metallicity Distributions of the Faintest Dwarf Galaxies

最暗矮星系的金属丰度分布

• 批准号: 2307599
• 负责人: Alexander Ji
• 金额: $ 45.92万
• 依托单位: University of Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2307599&HistoricalAwards=false
• 关键词: Metallicity; Distributions; Faintest; Dwarf; Galaxies

Ultra-faint dwarf galaxies (UFDs) appear to be the oldest, the most dark matter dominated, and the most metal-poor galaxies known. They appear to have formed all of their stars during the universe’s first 1-2 billion years of existence. As such, their stellar populations retain important information concerning processes at work during this early epoch, including the formation of the first generation of stars (Population III) and reionization. While high redshift UFDs are too faint to be studied by even the JWST, nearby examples should in principle be capable of yielding enough information to reconstruct their formation history and constrain galaxy formation. The principal investigator (PI) and his team will use deep spectroscopy and photometry obtained with the Magellan telescope to derive metallicities of 50-200 Main-Sequence turn-off (MSTO) stars for each of four nearby UFDs, more than doubling the number with measured chemical abundances. Analysis of the resulting metallicity distribution functions (MDFs) promises to yield precise star formation histories for these objects and thus provide important constraints on the formation of the first galaxies. An exciting secondary goal of this work is the possibility of detecting individual Population III stars among the observed MSTO stars and constraining their mass function. This award will support the training of a graduate student as well as research experiences for underrepresented undergraduate students. The PI will also implement a series of talks during the summer for undergraduate researchers.The researchers will obtain deep spectroscopy capable of enabling metallicity measurements for 50- 200 MSTO stars in each of the targeted UFD galaxies. This will result in the largest metallicity sample to date for chemical evolution modeling of these systems. The team will break age-metallicity degeneracies in isochrone-based star formation histories, which will enable sub-gigayear age precision for individual MSTOs. Ages and metallicities will be determined by simultaneously fitting stellar photometry and line equivalent widths. These will lead to the best-measured formation histories of UFDs, which will make the data invaluable as tests of chemical evolution or hydrodynamic galaxy formation simulations. These formation histories will advance understanding of the edge of galaxy formation by showing how quickly star formation is halted in the faintest dwarf galaxies. Given the very low UFD stellar masses and large number of metallicity measurements, there is also a substantial chance to discover a surviving Population III star, which would be the first of its kind.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.

超品种矮人的星系（UFD）似乎是最古老的，最暗的人是众所周知的，最贫穷的星系在宇宙存在的前10-2亿年中形成了所有恒星。他们出色的人口重要的信息G过程在恒星的早期时期（Poption III）和电源均已进行。限制星系的形成。 。这将支持培训的本科生。对于这些系统的化学演变，基于恒星的形成历史，可以使单个MSTOS的近视年龄精确拟合。这些形成的山山的构造是在最淡淡的矮人星系中逐渐停止的。 III星，这将是渴望的。