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

该奖项全部或部分根据2021年美国救援计划法案（公法117-2）资助。X射线联星（XRB）由一颗中子星星或黑洞组成，它们正在从近伴星星星上积极吸积气体;这种吸积是X射线发射的原因。特别令人感兴趣的是高质量X射线双星（HMXB），其中伴星星星的质量超过太阳的8倍，因为它们将成为双黑洞或中子星，当它们合并时能够产生可探测的引力波。XRB辐射的高能光子也可以加热星系的气体储存器，足以“制动”星星的形成，特别是在小的，金属贫乏的星系中，这些星系在高红移中占主导地位。此外，来自第一代恒星的HMXB可能有助于重建早期宇宙。因此，XRB在星系的形成和演化中发挥了重要作用。为了更好地了解XRB，需要评估它们如何受到其环境的年龄和金属含量的影响。该项目将描述具有一系列化学丰度、星星形成历史（SFH）和年龄的局部星系样本中XRB种群的特征，以评估任何此类依赖性。该提案将支持每年指导两名本科生研究人员，以及天文学暑期学校（Cal Poly PASS），每年将培训大约10名本科生，全部来自代表性不足或边缘化的群体。由首席研究员（PI）和学生进行的研究将确定XRB X射线光度函数（XLF）的详细形状，同时控制环境金属丰度，SMH，和恒星年龄的个别XRB在48个附近的星系使用多波长档案数据。XLF的形状预计会随着金属丰度和恒星年龄的变化而变化，沿着，在局部低质量、低金属丰度的星系中，HMXB形成效率会发生实质性（和随机性）变化，这些星系与高红移的年轻星系类似。理解XLF形状和XRB缩放关系中固有的分散对于约束XRB群体合成模型（例如）详细的星系演化模拟，更清楚地了解宇宙时间内星星形成的抑制，以及更好地了解这些物体如何有助于宇宙的再电离。这个LEAPS-MPS研究计划代表了对XRB及其环境的第一次千分之一秒尺度的系统研究。丰富的，公开可用的档案观测附近的星系提供了额外的机会，在加州理工大学波莫纳分校的本科生参与研究。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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.