Baryon Cycles in the Biggest Galaxies

为了充分了解星系的演化，我们必须确定形成它们的主要过程。其中一个过程是“重子循环”，类似于地球上的水和碳循环，即气体在星系的星际（ISM）和星系周围介质（CGM）之间循环，这是由各种加热（例如超新星和射电喷流）和冷却机制决定的，在这个过程中形成了一个复杂而动态的星系“大气”。这个过程的细节控制着气体流入或流出星系，因此恒星的形成和星系环境的化学富集。这项研究将使用详细的数值模拟来了解星系大气的动力学。研究人员将通过一个双重用途的网站来支持公共教育：一个以计算机模拟的可视化为特色，另一个以交互式电子文本为特色，向学生介绍星系大气的物理学。支持1名博士后。本研究将通过确定其松弛的准流体静力平衡状态以及由于能量输入（如超新星和活动星系核）和质量吸积而偏离这些状态来研究星系大气的动力学-即ISM和CGM的组合。三大类数值模拟将试图：(1)更好地理解从CGM到ISM的低温气体的凝结和随后的“降水”如何取决于（例如）局部气体湍流、大尺度熵梯度、扰动、浮力以及冷却和自由落体时间尺度的比例；(2)首次在高空间分辨率上研究了窄射电喷流（开口角为100）通过加热CGM并在大尺度上降低两者的压力和密度间接抑制ISM中恒星形成的能力。来自ISM星系的气体可能随后被超新星推入CGM；(3)更好地理解由活动星系核膨胀的“气泡”产生的CGM中的熵梯度影响星系范围内恒星形成的能力，以及这一过程如何依赖于星系晕质量（以及CGM的“宇宙学”熵含量）。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。

In order to fully understand galaxy evolution one must identify the major processes that shape them over time. One such process is the “baryon cycle”, analogous to the Water and Carbon cycles on Earth, whereby gas cycles between a galaxy’s interstellar (ISM) and circum-galactic media (CGM) as determined by various heating (e.g., supernovae and radio jets) and cooling mechanisms, in the process forming a complex and dynamic galactic “atmosphere”. The details of this process regulates gas flows into or out of the galaxy and thus star formation and chemical enrichment of a galaxy’s environment. This research will use detailed numerical simulations to understand the dynamics of galactic atmospheres. The investigators will support public education through a dual-purpose website: one featuring visualizations of computer simulations and a second featuring interactive e-text to introduce students to the physics of galaxy atmospheres. One postdoc will be supported.This research will investigate the dynamics of galaxy atmospheres – i.e., the combined ISM and CGM – by determining its relaxed quasi-hydrostatic equilibrium states and the departures from these states due to energy input (e.g., supernovae and active galactic nuclei) and mass accretion. Three broad groups of numerical simulations will attempt to: (1) better understand how the condensation and subsequent “precipitation” of cool gas from the CGM to the ISM depends on (e.g.) the local gas turbulence, large-scale entropy gradients, perturbations, buoyancy, and the ratio of cooling and free-fall timescales; (2) make the first high spatial resolution study of the ability of narrow (opening angle 10o) radio jets to indirectly suppress star formation in the ISM by heating the CGM and lowering the pressure and density of both on large scales. Gas from the galaxy ISM may be subsequently pushed into the CGM by supernovae; (3) better understand the ability of entropy gradients in the CGM produced by active galactic nuclei inflated “bubbles” to influence galaxy wide star formation, and how this process might depend on the galaxy’s halo mass (and the CGM’s “cosmological” entropy content).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.