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)，以突破我们基础物理和天体物理知识的界限。CMB第四阶段的一个组成部分是超深探测，它将以前所未有的灵敏度在度角尺度上测量CMB的偏振。超深探测的偏振图将是搜索原始引力波的有力工具，只要这些图没有由于仪器系统误差而受到污染。该奖项将支持利用从当前一代CMB望远镜中学到的经验，开发和分析针对超深探测的系统学的详细模拟。这些模拟将为CMB-S4的设计提供参考，并为开发缓解技术提供一个试验场。该计划还将支持辛辛那提大学物理桥项目即将到来的研究生的科学计算训练营，确保这些学生拥有在研究生院取得成功和未来职业生涯所必需的工具。原始引力波是对膨胀理论的预测，这是对我们宇宙初始条件的主要解释。寻找这些引力波最有效的技术是利用CMB的B模(旋度型)偏振，它不是由密度微扰引起的。然而，原始的B模偏振必须非常微弱，因此一个关键的挑战是控制所有可能泄漏温度或E模波动到B模的影响。还有必要将原始的CMB信号从透镜引起的次级各向异性和银河前景发射中分离出来；这些挑战需要合并角度尺度上的数据和高保真的观测频率。过去和现在的CMB实验都证明了对系统误差的良好控制，但CMB-S4的原始灵敏度要求相应较低的系统学水平。CMB-S4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，但有必要进行详细的模拟，以将这些限制与仪器设计和校准的规范联系起来。该奖项支持的工作将通过一系列有针对性的模拟集来建立这些联系。生成和分析这些模拟的过程也将有助于CMB-S4数据管道的开发。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.