LEAPS-MPS: Investigating Metallicity and Stellar Age Effects on X-ray Binary Populations

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。X射线双星(XRBs)由一颗中子星或黑洞组成，该中子星或黑洞正在积极地吸积来自亲密伴星的气体；这种吸积是发射X射线的原因。特别令人感兴趣的是高质量X射线双星(HMXB)，其中的伴星质量是太阳的8倍以上，因为它们将成为双星黑洞或中子星，当它们合并时能够产生可探测到的引力波。XRB辐射的高能光子也可以充分加热星系的储气罐，对恒星的形成起到“刹车”的作用，特别是在占主导地位的高红移的小的贫金属星系中。此外，来自第一代恒星的HMXB可能帮助重新电离了早期的宇宙。因此，XRBs在星系的形成和演化中发挥了重要作用。为了更好地理解XRBs，需要评估它们是如何受到其环境的年龄和金属丰度的影响的。这个项目将在具有一系列化学丰度、恒星形成历史(SFH)和年龄的局部星系样本中表征XRB群体，以评估任何此类依赖。该提案将支持每年两名本科生研究人员的指导，以及一所天文学暑期学校(Cal Poly Pass)，该学校每年将培训大约10名本科生，所有人都来自代表性不足或被边缘化的群体。首席调查员(PI)和学生开展的研究将确定XRB X射线光度函数(XLF)的详细形状，同时利用多波长档案数据控制环境金属丰度、SMH和附近八个星系内单个XRB的恒星年龄。XLF的形状预计将随着金属丰度和恒星年龄的变化而演变，以及局部低质量、低金属丰度星系中HMXB形成效率的实质性(和随机)变化，这些星系类似于在高红移时发现的年轻星系。了解XRB标度关系中固有的XLF形状和散射对于限制(例如)中使用的XRB布居合成模型将是重要的。详细的星系演化模拟，更清楚地了解宇宙时间内恒星形成的抑制，以及这些天体如何对宇宙的再电离做出贡献。LEAPS-MPS研究计划是首次在亚千级尺度上对XRBs及其环境进行系统研究。对附近星系丰富的、可公开获取的档案观测为加州大学保利·波莫纳分校的本科生提供了更多参与研究的机会。这一奖项反映了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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). X-ray binaries (XRBs) consist of a neutron star or black hole that is actively accreting gas from a close companion star; this accretion is responsible for the emission of X-rays. Of particular interest are high-mass X-ray binaries (HMXBs), in which the companion star is more than 8 times the Sun's mass, as these will become binary black holes or neutron stars, capable of producing detectable gravitational waves when they merge. The high-energy photons radiated by XRBs can also heat a galaxy's gas reservoir sufficiently to "act as a brake" on star formation, particularly in the small, metal poor galaxies that dominate at high redshift. Moreover, HMXBs from the first generation of stars likely helped reionize the early universe. XRBs have thus played a significant role in the formation and evolution of galaxies. A better understanding of XRBs requires an appraisal of how they are affected by the age and metallicity of their environment. This project will characterize XRB populations in a sample of local galaxies having a range of chemical abundance, star formation history (SFH), and age to assess any such dependence. The proposal will support the mentoring of two undergraduate researchers each year, as well as an astronomy summer school (Cal Poly PASS) that will train roughly ten undergraduates per year, all drawn from under- represented or marginalized groups.Research carried out by the principal investigator (PI) and students will determine the detailed shape of the XRB X-ray luminosity function (XLF) while controlling for environmental metallicity, SMH, and stellar age for individual XRBs within forth-eight nearby galaxies using multiwavelength archival data. The shape of the XLF is expected to evolve with metallicity and stellar age, along with substantial (and stochastic) variations in HMXB formation efficiency in local low-mass, low- metallicity galaxies that serve as analogs to the young galaxies found at high redshift. Understanding the XLF shape and scatter inherent in XRB scaling relations will be important for constraining XRB population synthesis models used in (e.g.) detailed galaxy evolution simulations, a clearer understanding of star formation suppression over cosmic time, and for a better sense of how these objects contribute to the reionization of the universe. This LEAPS-MPS research program represents the first systematic study of XRBs and their environments on sub-kiloparsecscales. The rich, publicly available archival observations of nearby galaxies provide additional opportunities for undergraduate students at Cal Poly Pomona to participate in research.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.