CMB Polarization Foreground Effects on B-modes and Lensing

科学家们在20世纪60年代首次观测到宇宙大爆炸遗留下来的宇宙微波背景。在未来的十年里，新的和精确的测量可能会让天文学家利用宇宙微波背景来寻找原始引力波的微弱迹象。从理论上讲，这些波应该是宇宙最初迅速膨胀时的量子涨落产生的，发现它们将是对这一观点的革命性证实。然而，这些引力波的迹象将被两种效应所掩盖：引力透镜效应和银河系污染。透镜效应是宇宙中星系和暗物质的引力作用造成的微波背景光的扭曲。我们银河系中的气体和尘埃进一步污染了我们的视野。在这个项目中，研究人员将模拟气体和尘埃，并研究透镜畸变的缓解，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激动人心的发展达到更广泛的社区，这个项目的重点是通过公开演讲和活动，大学水平的课程开发和高质量的STEM学生指导吸引新的学生到STEM学科。银河系前景污染比可能的极化（“b模式”）引力波信号更大，但太小太微弱，无法被普朗克卫星很好地表征。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)继续发展基于分析细丝的前景模型，(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模测量、透镜重建和去光的含义，并将增强对观测到的偏振前景和星际介质特性的物理基础的理解。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。

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.