Toward physically-predictive modeling of massive black hole growth and feedback in galaxy formation

天体物理学中的一个长期问题是了解星系在其一生中是如何形成和发展的。这样的理解对于揭示我们的宇宙是如何进化的以及洞察我们银河系的起源是必要的。几乎所有的星系似乎都有大质量的中央黑洞(BHS)-很多都有比我们银河系的大得多的中心黑洞。观测显示星系和大质量的BHS之间有着密切的联系。然而，大规模黑洞的形成，它们是如何生长的，以及它们如何通过反馈影响星系的生命周期，人们仍然知之甚少。我们在理解由引力扭矩将气体从星系尺度输送到星系核中，以及对活动星系核(AGN)驱动的星系尺度风的观测方面取得的基本进展正在改变我们对黑洞增长和反馈的理解，并使我们能够在回答这些问题方面取得决定性的进展。这个项目是一个多尺度的模拟计划，建立在这些突破和调查人员之前的分析建模的基础上。该项目将从星系和星系核中黑洞增长和反馈的超高分辨率模拟开始(低至约0.01pc)。该小组还将从他们的模拟中产生可视化效果，以支持他们的教育和外展工作。这些可视化将包括与时间相关的动画和3-D互动探索模块，将在芝加哥阿德勒天文馆的空间可视化实验室展出。由该奖项资助的博士后PI和该团队中的研究生将每月在阿德勒参加一次“天文对话”，每小时吸引多达300名所有年龄段的参观者。通过这些天文学对话，该团队将向公众解释黑洞在星系演化中的迷人作用。他们还将把教育材料整合到由西北大学人才发展中心为高中生开设的为期一年的计算天体物理学课程中。在这门课程中，学生们学习用Python编写代码，并将这些技能应用于使用他们选择的大型天文数据集进行独立研究项目。视频(将包括解释模拟背后的科学以及它们是如何创建的)将向学生介绍一种新的模拟数据集，他们可以为他们的项目工作。研究人员还将继续让本科生积极参与他们的研究。该项目的模拟将包括一个显式的恒星反馈模型，该模型自我一致地产生多相星际介质和恒星形成驱动的外流。这些模拟将用于研究具有代表性的一组模型星系中黑洞吸积的物理和由活动星系核驱动的广角流出的相互作用，包括活动星系核对气体和恒星形成的影响，并校准活动星系核燃料和反馈模型，用于宇宙学模拟。然后将在宇宙学模拟中实施BHS(大约1到100个pC分辨率)，使PI能够调查大质量BHS的起源(种子模型和超爱丁顿吸积的必要性)，星系-黑洞标度关系的出现，活动星系核反馈在大质量星系熄灭恒星形成中的作用，以及活动星系核外流对晕气体的影响。一种从小到大的系统方法，将使PI能够解决以前在星系和宇宙尺度上模拟BHS的主要不确定性。为了最大限度地发挥模拟的影响，辐射传递计算将被紧密地纳入该项目，该计算将允许通过大量当前和未来的观测直接测试结果。这项多尺度BH研究的目标是使BHS的预测能力达到与恒星形成的可能性相当的水平。将开发的亚分辨率黑洞模型将在星系规模和宇宙模拟中实现更具预测性的黑洞模型-从而减轻目前星系形成理论中最大的不确定性。

A longstanding problem in astrophysics is to understand how galaxies form and develop throughout their lifetimes. Such understanding is necessary to uncover how our Universe evolved and to gain insight into the origin of our own Milky Way Galaxy. Nearly all galaxies appear to have massive central black holes (BHs)---many with ones much, much larger than our Milky Way's. Observations reveal close connections between galaxies and massive BHs. However, the formation of massive BHs, how they grow, and how they affect the galaxy life cycle via feedback remain poorly understood. Fundamental advances in our understanding of gas transport from galactic scales into galactic nuclei by gravitational torques and in observations of galaxy-scale winds driven by active galactic nuclei (AGN) are transforming our understanding of BH growth and feedback and are enabling definitive progress in answering these questions. This project is a multi-scale simulation program that builds on these breakthroughs and on the investigators' previous analytic modeling. The project will begin with ultra-high resolution simulations (down to about 0.01 pc) of BH growth and feedback in galaxies and galactic nuclei.The group will also produce visualizations from their simulations specifically designed to support their education and outreach efforts. The visualizations, which will include both time-dependent animations and 3-D interactive exploration modules, will be displayed at the Space Visualization Laboratory at the Adler Planetarium in Chicago. The PI, the postdoc funded by this award, and graduate students in the group will volunteer once a month for "astronomy conversations" at Adler, which attract up to 300 visitors per hour of all ages. Through these astronomy conversations, the team will explain the fascinating roles of black holes in galaxy evolution to the public. They will also integrate educational materials into a year long computational astrophysics course for high school students offered through Northwestern's Center for Talent Development. In the course, students learn to code in Python and apply these skills to pursuing an independent research project using a large astronomical data set of their choosing. Videos (which will include explanations of the science behind the simulations and of how they were created) will introduce the students to a new kind of simulated data set that they can work on for their projects. The investigators will also continue to actively involve undergraduate students in their research.The project's simulations will include an explicit model for stellar feedback that self-consistently produces a multiphase interstellar medium and star-formation driven outflows. These simulations will be used to study the physics of BH accretion and the interaction of wide-angle AGN-driven outflows in a representative set of model galaxies, including the effects of AGN on gas and star formation, and to calibrate AGN fueling and feedback models for use in cosmological simulations. BHs will then be implemented in cosmological simulations (about 1 to 100 pc resolution) that will allow the PI to investigate the origin of massive BHs (seed models and the need for super-Eddington accretion), the emergence of galaxy-BH scaling relations, the role of AGN feedback in quenching star formation in massive galaxies, and the effects of AGN outflows on halo gas. A systematic approach, building up from small to larger scales, will enable the PI to resolve the main uncertainties of previous simulations of BHs on galaxy and cosmological scales. To maximize the impact of the simulations, radiative transfer calculations, which will allow a direct test of the results with a wealth of current and future observations, will be tightly incorporated in the project. The goal of this multi-scale BH study is to achieve for BHs a level of predictive power comparable to what has become possible for star formation. The sub-resolution BH models that will be developed will enable substantially more predictive BH modeling in galaxy-scale and cosmological simulations---thus alleviating arguably the largest uncertainty in current galaxy formation theories.