Collaborative Research: Cosmic Ray Feedback from Plasma to Circumgalactic Scales

通过反馈对恒星形成的自我调节，星系风的发射，以及星系与其周围星系介质之间的相互作用，是星系形成和演化的基本和相互关联的组成部分。反馈的主要因素是星际气体、辐射和磁化宇宙射线的热能和湍流能量。宇宙射线与背景介质交换动量和能量，与电离气体的耦合可能比光子更好，但将它们纳入星系模型所需的物理和计算工具仍处于早期阶段，尚未得到充分研究。这个项目通过开发和实施研究宇宙线等离子体物理的新工具来解决这一“宇宙线缺口”，因为它应用于恒星形成反馈。该小组将组织外联活动，以提高一般的科学素养，包括天文馆表演和公开讲座系列。本科生和研究生将参与研究的各个方面，提供广泛的专业培训。研讨会将促进在宇宙射线物理学、磁场、星际和星系团内反馈方面有着密切联系的参与者之间的合作。合作者在等离子体天体物理理论、计算天体物理、宇宙线物理和星系演化的天体物理方面具有互补和重叠的专业知识。这项研究将涵盖从亚AU微观等离子体尺度到100kpc环星系尺度的长度尺度上的过程，并将最先进的流体动力学和混合流体动力学数值模拟与分析理论相结合。研究目标包括：(1)找到在恒星反馈模型中包括宇宙射线的改进处方；(2)量化解开星系中星际气体所需的宇宙射线流量的“爱丁顿极限”；(3)建立包括宇宙射线的环星系介质模型；(4)预测宇宙射线的作用。为了与数据进行比较，研究人员将计算带有宇宙射线的模型的非热伽马射线和无线电同步辐射；伽马射线结果将用于解释与费米的观测。这一裁决反映了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 self-regulation of star formation through feedback, the launching of galactic winds, and the interactions between galaxies and their circum-galactic medium, are fundamental and interrelated components of galaxy formation and evolution. The primary agents of feedback are the thermal and turbulent energy of interstellar gas, radiation, and magnetized cosmic rays. Cosmic rays exchange momentum and energy with the background medium and may be better coupled to the ionized gas than are the photons, but the physical and computational tools needed to include them in galaxy models are still at an early stage, and have not yet been fully studied. This project addresses this “cosmic ray gap” by developing and implementing new tools for studying the plasma physics of cosmic rays as it applies to star formation feedback. The team will organize outreach events to improve general scientific literacy, including planetarium shows and public lecture series. Undergraduates and graduate students will be involved in all aspects of the research, providing broad professional training. Workshops will foster collaborations among participants who share closely related interests in the physics of cosmic rays, magnetic fields, and interstellar and intra-cluster feedback.The collaborators have complementary and overlapping expertise in plasma astrophysics theory, computational astrophysics, cosmic ray physics, and the astrophysics of galaxy evolution. This study will cover processes on length scales from the sub-AU microscopic plasma scales to the 100 kpc circum-galactic scales, and will combine state of the art fluid dynamical and hybrid fluid–kinetic numerical simulations with analytical theory. The research goals include: (1) find improved prescriptions for including cosmic rays in models of stellar feedback; (2) quantify an “Eddington Limit” for the cosmic ray flux necessary to unbind the interstellar gas in a galaxy; (3) construct models of the circum-galactic medium that include cosmic rays; (4) make predictions for observational tests of the role of cosmic rays. For comparison with data, the investigators will calculate the non-thermal gamma-ray and radio synchrotron emission from models with cosmic rays; the gamma-ray results will be used to interpret observations with Fermi.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.