Understanding instrumental systematics for the CMB-S4 ultra-deep survey

CMB Stage-4实验是下一代望远镜阵列，将测量宇宙微波背景（CMB），以推动我们对基础物理学和天体物理学知识的边界。CMB第四阶段的一个组成部分是超深测量，它将以前所未有的灵敏度测量CMB的偏振度。只要极化图不受仪器系统误差的影响，超深探测得到的极化图将是寻找原始引力波的有力工具。该奖项将支持开发和分析针对超深调查系统学的详细模拟，利用从当前一代CMB望远镜中吸取的经验教训。模拟将为CMB-S4的设计提供信息，并为开发缓解技术提供试验场。该项目还将为辛辛那提大学物理学桥梁项目的研究生提供科学计算训练营，确保这些学生拥有在研究生院和未来职业生涯中取得成功的必要工具。原始引力波是暴胀理论的预测，暴胀理论是对我们宇宙初始条件的主要解释。寻找这些引力波的最强大的技术是使用CMB的B模式（卷曲型）偏振，它不是由密度扰动引起的。然而，原始B模式偏振必须非常微弱，因此关键的挑战是控制可能将温度或E模式波动泄漏到B模式的所有效应。 也有必要将原始CMB信号与透镜诱导的次级各向异性和银河前景发射分开;这些挑战需要在角尺度上组合数据并以高保真度观察频率。过去和目前的CMB实验已经证明了对系统误差的良好控制，但是CMB-S4的原始灵敏度需要相应的较低水平的系统学。CMB-S4的预测工作为地图中可接受的虚假污染水平提供了指导方针，但需要进行详细的模拟，以将这些限制与仪器设计和校准规范联系起来。该奖项支持的工作将通过一系列有针对性的模拟集建立这些联系。该奖项反映了NSF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。

The CMB Stage-4 experiment is a next-generation array of telescopes that will measure the Cosmic Microwave Background (CMB) to push the boundaries of our knowledge of fundamental physics and astrophysics. One component of CMB Stage-4 is the ultra-deep survey, which will measure the polarization of the CMB at degree angular scales with unprecendented sensitivity. Polarization maps from the ultra-deep survey will be a powerful tool to search for primordial gravitational waves, so long as the maps are free of contamination due to instrumental systematic errors. This award will support development and analysis of detailed simulations targeting systematics for the ultra-deep survey, using lessons learned from the current generation of CMB telescopes. The simulations will inform the design of CMB-S4 and provide a testing ground for development of mitigation techniques. This program will also support a scientific computing bootcamp for incoming graduate students in the University of Cincinnati physics bridge program, making sure that these students have necessary tools for success in graduate school and their future careers.Primordial gravitational waves are a prediction of inflationary theories, which are the leading explanation for the initial conditions of our universe. The most powerful technique to search for these gravitational waves is using the B-mode (curl-type) polarization of the CMB, which is not sourced by density perturbations. However, primordial B-mode polarization must be very faint, so a critical challenge is to control all effects that might leak temperature or E-mode fluctuations into B-modes. It is also necessary to separate primordial CMB signals from lensing-induced secondary anisotropies and Galactic foreground emission; these challenges require combining data across angular scales and observing frequencies at high fidelity. Past and current CMB experiments have demonstrated good control over systematic errors, but the raw sensitivity of CMB-S4 requires correspondingly lower levels of systematics. The CMB-S4 forecasting effort has provided guidelines for the acceptable level of spurious contamination in the maps, but detailed simulations are necessary to connect these limits to specifications on instrument design and calibration. The work supported by this award will establish these connections through a series of targeted simulation sets. The process of generating and analyzing these simulations will also contribute to the development of CMB-S4 data pipelines.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.