CAREER: Mass Measurements in the Galaxy

本奖项全部或部分由《2021年美国救援计划法案》（公法117- 2）资助。大质量恒星，即那些质量超过太阳十倍的恒星，由于寿命短，在局部星系中相对较少。然而，它们在星系演化中发挥了巨大的作用。例如，它们的能量输出在很大程度上决定了星际介质的热力学，并有助于确定分子云中恒星形成的时间尺度。通过核心坍缩的超新星和由中子星和黑洞组成的奇异双星系统的合并，大质量恒星也负责创造和分散星系中相当一部分重元素（岩石行星和生命所必需的）——它们本身就是大质量恒星演化的终点。第一代大质量恒星也可能在大爆炸后不久电离了星系间介质。拟议的研究将使用来自阿塔卡马大型亚/毫米波阵列（ALMA）的新数据和档案数据来帮助确定大质量恒星形成的主要机制以及它们的环境所起的作用，这两者都不完全被理解。该项目还将支持一名博士后研究员和一名研究生的研究活动，以及首席研究员开发和分发基于python的光学/无线电数据分析工具和教程的努力。研究小组将利用ALMA在银河系的圆盘和中心的观测，得出高质量年轻恒星天体（HMYSOs）样本的精确质量——大质量恒星的前身——以及同一星团内低质量原恒星的精确质量。虽然许多特大myso似乎是通过从其相关的圆盘吸积气体而增长的，但有证据表明，大质量恒星也可以通过合并或由流入驱动的不稳定性而增长。为了区分这些可能性，他们将首先通过分析由盐（NaCl和KCl）发射谱线追踪的圆盘运动学来测量hmyso的动力质量。这代表了一种在大质量恒星生命开始时测量质量的新方法，因为这些线似乎在ALMA档案中经常被探测到。恒星相互作用、湍流流入和盘状吸积的相对重要性需要确定hmyso附近低质量原恒星群的性质。同样的ALMA观测将使这种普查成为可能。将尘埃发射图与使用NH3或CH3CN线的温度测量相结合，研究小组将测量hmyso周围原恒星的光度函数和空间分布。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117- 2). Massive stars, i.e., those more than ten times the Sun’s mass, are comparatively rare in local galaxies due to their short lifetimes. They nevertheless play an outsized role in galaxy evolution. Their energy output, for example, largely determines the thermodynamics of the interstellar medium and helps set the timescale for star formation in molecular clouds. Massive stars are also responsible for the creation and dispersal of a significant fraction of heavy elements (necessary for rocky planets and life) in galaxies through core-collapse supernovae and mergers of exotic binary systems comprised of neutron stars and black holes - themselves end-points of massive star evolution. The first generation of massive stars may also have ionized the intergalactic medium soon after the Big Bang. The proposed research will use new and archival data from the Atacama Large Sub/Millimeter Array (ALMA) to help determine the dominant mechanism(s) involved in the formation of massive stars and the role played by their environments, both incompletely understood. This project will also support research activities by a postdoctoral researcher and a graduate student, as well as efforts by the principal investigator to develop and distribute python based optical/radio data analysis tools and tutorials.The research team will derive accurate masses for a sample of High Mass Young Stellar Objects (HMYSOs) - the predecessors of massive stars - as well as lower mass protostars within the same cluster using ALMA observations in the Milky Way’s disk and center. While many HMYSOs appear to grow by accreting gas from their associated disks, there exists evidence that massive stars can also grow through mergers or inflow-driven instabilities. To distinguish between these possibilities, they will first measure dynamical masses of HMYSOs through the analysis of disk kinematics as traced by salt (NaCl and KCl) emission lines. This represents a novel approach to measure masses at the start of massive stars’ lives as these lines appear to be commonly detected for HMYSOs in the ALMA archive. The relative importance of stellar interactions, turbulent inflow, and disk-mediated accretion requires determining properties of lower-mass proto-stellar populations in the vicinity of the HMYSOs. The same ALMA observations will enable such censuses. Combining dust emission maps with temperature measurements using NH3 or CH3CN lines, the team will measure the luminosity function and the spatial distribution of protostars surrounding HMYSOs.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.