Star Formation, ISM, and Winds in Bursty vs. Steady Galaxies

在星系中，只要分子气体变得足够寒冷和稠密，引力就会变得不稳定，从而引发分裂和随后的坍缩，恒星就会形成。然而，恒星一旦形成，就会通过超新星、紫外线辐射和快速恒星风注入的能量对周围环境产生深远的影响，这些过程统称为“恒星反馈”。恒星反馈可以抑制恒星形成速率（SFR），调节星系的整体质量增长，并塑造其多相星际介质（ISM）。虽然在模拟恒星反馈方面已经取得了很大的进展，但以前的工作主要集中在类似银河系的系统上，那里的SFR相当恒定。然而，在低质量和/或高红移星系中，恒星形成往往具有高度偶发性或“突发”的SFRs，在那里，恒星反馈可能以与局部螺旋完全不同的方式工作。首席研究员和团队将把恒星反馈理论从“稳定”系统扩展到爆发系统，特别是最近在高红移发现的小而富含气体的例子，这些例子很可能是银河系系统的祖先，这是最先进的地面和太空天文台许多观测研究的重点。除了一名博士后之外，该奖项还将支持三名本科生研究人员的指导，芝加哥阿德勒天文馆的外展活动和其他公共活动，以及对FIREFLY（一个交互式科学可视化工具）的改进。拟议的研究将集中在一套大的放大模拟上，这些模拟解决了宇宙学背景下单个星系的ISM，并自洽地模拟了从爆发星系到稳定星系的转变。模拟包括从矮星到超级l *星系中发现的所有主要恒星形式。该项目将重点研究三个核心科学问题：(1)“平衡盘”或“压力平衡”模型对kennicut - schmidt恒星形成定律起源的适用性；(2)ISM的动力学和热力学性质及其与环星系介质的关系；(3)爆发星系与稳定星系中星系风和星系喷泉的发射。模拟的变体将包括额外的物理过程（例如，磁场、宇宙射线和非平衡ISM化学），以测试结果如何依赖于这些额外的变量。将进行观测预测，以在不同的条件下测试模拟预测。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。

Stars form in galaxies wherever molecular gas becomes sufficiently cold and dense to become gravitationally unstable, which initiates fragmentation and subsequent collapse. Once formed, however, stars can profoundly affect their surroundings through the energy injected by supernovae, ultraviolet radiation, and fast stellar winds, processes collectively referred to as "stellar feedback." Stellar feedback can suppress the star formation rate (SFR), regulate the overall mass growth of a galaxy, and shape its multi-phase interstellar medium (ISM). While there has been much progress in modeling stellar feedback, previous work has focused primarily on Milky Way-like systems, where the SFR is fairly constant. However, star formation in low-mass and/or high-redshift galaxies tend to have highly episodic or "bursty" SFRs, where stellar feedback may work in fundamentally different ways relative to local spirals. The principal investigator and team will extend stellar feedback theory from "steady" systems to bursty ones, and in particular, the small and highly gas rich examples recently found at high-redshift that are likely the progenitors of Milky Way-like systems, and which are the focus of many observational studies by state-of-the-art ground- based and space-based observatories. In addition to a postdoc, this award will support the mentoring of three undergraduate researchers, outreach events at Chicago's Adler Planetarium and other public events, and improvements in FIREFLY, an interactive scientific visualization tool.The proposed research will be centered on a large suite of zoom-in simulations that resolve the ISM of individual galaxies in a cosmological context, and which self-consistently model the transition from bursty to steady galaxies. The simulations include all the main forms of stellar found in galaxies from dwarfs to super-L*. The project will focus on three core science issues: (1) the applicability of “equilibrium disk” or “pressure balance” models for the origin of the Kennicutt-Schmidt star formation law, (2) the dynamical and thermodynamic properties of the ISM and its relationship to the circumgalactic medium, and (3) the launching of galactic winds and galactic fountains in bursty vs. steady galaxies. Variants of the simulations will include additional physical processes (e.g., magnetic fields, cosmic rays, and non-equilibrium ISM chemistry) to test how the results depend on these additional variables. Observational predictions will be made to test the simulation predictions in the different regimes.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.