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

恒星在星系中形成，分子气体变得足够冷和密集，变得重力不稳定，这引发了碎片和随后的坍缩。然而，一旦形成，恒星就可以通过超新星、紫外线辐射和快速恒星风注入的能量深刻地影响周围环境，这些过程统称为“恒星反馈”。恒星反馈可以抑制星星形成率（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取得了很大进展，但以前的工作主要集中在类似银河系的系统上，其中SFR相当恒定。然而，低质量和/或高红移星系中的星星形成往往具有高度的偶发性或“突发性”的SFR，其中恒星反馈可能以相对于本地螺旋的根本不同的方式工作。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型和高度气体丰富的例子，这些例子可能是银河系系统的祖先，并且是最先进的地面和空间观测站的许多观测研究的重点。除了博士后，该奖项将支持三名本科生研究人员的指导，在芝加哥的阿德勒天文馆和其他公共活动的推广活动，以及互动科学可视化工具FIREFLY的改进。拟议的研究将集中在一个大型的放大模拟套件上，解决宇宙学背景下单个星系的ISM，并且自洽地模拟了从爆发到稳定星系的转变。模拟包括从矮星系到超L * 星系中发现的所有主要形式的恒星。该项目将侧重于三个核心科学问题：（1）“平衡盘”或“压力平衡”模型对肯尼库特-施密特星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），以测试结果如何取决于这些额外的变量。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。

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.