CMB Polarization Foreground Effects on B-modes and Lensing

科学家在20世纪60年代首次观察到大爆炸遗留下来的宇宙微波背景。 在接下来的十年里，新的精确测量可能会让天文学家利用宇宙微波背景找到原始引力波的微弱迹象。 从理论上讲，这些波应该是宇宙在最初时刻迅速膨胀时的量子涨落引起的，找到它们将是对这一想法的革命性证实。 然而，这些引力波的迹象将被两种效应所掩盖：引力透镜和银河系污染。 透镜效应是指微波背景辐射的光线在宇宙中星系和暗物质的引力作用下发生的扭曲。 我们银河系中的气体和尘埃会进一步污染我们的视野。 在这个项目中，研究人员将对气体和尘埃进行建模，并研究如何减轻透镜扭曲，以帮助未来探测原始引力波的尝试。 该项目将资助本科生和研究生的研究和培训。 为了确保早期宇宙研究的令人兴奋的发展能够惠及更广泛的社区，该项目的重点是通过公开讲座和活动，大学课程开发，和高质量的STEM学生指导。银河系前景污染大于可能的偏振（“B模式”）的引力波信号，但太小，太微弱，无法很好地表征普朗克卫星。该项目建立在研究人员目前对这些前景污染物的建模基础上，以表征和避免这些问题。 这项工作将（1）继续发展一个分析性的基于磁流体动力学的前景模型，（2）使用磁流体动力学（MHD）计算机模拟湍流星际介质作为现实前景模拟的基础。 这些工具将用于研究B模式测量、透镜重建和去透镜的影响，并将增强对偏振前景和星际介质观测特性的物理基础的理解。该奖项反映了NSF的法定使命，并被认为值得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来支持。

Scientists in the 1960s first observed the background of cosmic microwaves left over from the Big Bang. In the coming decade, new and precise measurements may let astronomers use the cosmic microwave background to find faint signs of primordial gravitational waves. Theoretically, these waves should arise from quantum fluctuations as the Universe expanded rapidly in its first moments, and finding them would be a revolutionary confirmation of this idea. However, the signs of these gravitational waves will be obscured by two effects: gravitational lensing and Milky Way contamination. Lensing is the distortion of the microwave background's light by the gravitational pull of galaxies and dark matter throughout the Universe. Gas and dust in our own Milky Way galaxy then further contaminate our view. In this project researchers will model the gas and dust and investigate mitigation of the lensing distortions to aid future attempts at detection of primordial gravitational waves. The project will sponsor the research and training of students at the undergraduate and graduate level. To ensure that exciting developments in early-Universe research reach the broader community, this project focuses on attracting new students to STEM disciplines with public talks and events, college-level curriculum development, and high-quality STEM student mentoring.The Milky Way foreground contamination is larger than the possible polarization ("B-mode") signal of gravitational waves but is too small and too faint to be well characterized by the Planck satellite. This project builds on the researcher’s current modeling of these foreground contaminants to characterize and avoid these problems. The effort will (1) continue development of an analytic filament-based foreground model and (2) use magnetohydrodynamic (MHD) computer simulations of the turbulent interstellar medium as a basis for realistic foreground simulations. These tools will be used to investigate the implications for B-mode measurements, lensing reconstruction, and delensing, and will enhance understanding of the physical basis for observed properties of the polarization foreground and the interstellar medium.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.