The Hidden Lives of Massive Protostars: Fragmentation, Disks, and Feedback

虽然在开发低质量恒星形成过程的标准模型方面已经取得了相当大的进展，但我们离了解大质量恒星是如何形成的还很远。大质量恒星产生了宇宙中的大部分金属，通过电离辐射、风和超新星控制了星际和星系间介质的能量平衡，并通过与附近原行星盘的相互作用塑造了行星的形成。如果没有可靠的大质量恒星形成模型，就不可能理解这些过程。在这个项目中，Mark Krumholz博士（加州大学圣克鲁兹分校）将开发这样一个模型，使用分析调查和高分辨率模拟的补充工具，包括重力、辐射和磁流体动力学。作为这项研究的一部分，必须解决一些问题和问题。在大质量恒星形成的最初阶段，我们必须了解破碎过程。是什么物理机制控制着气体碎片的大小小于一个太阳质量，还是整体坍塌成一个大质量的恒星？一旦坍缩开始，任何模型都必须描述如何克服吸积的两个主要障碍，角动量和辐射压力。圆盘是一个可能的解决方案，因为它们重新分配角动量，同时它们的高不透明度保护气体免受辐射。这个项目的第二个重要部分是发展对大质量原恒星盘的理解。在大质量恒星形成过程的最后，是什么最终阻止了吸积并清除了剩余的气体？除了研究这些问题，并使用与这项研究相关的材料，Krumholtz博士还将根据他在监狱教育方面的十年经验，为加州圣克鲁斯附近监狱的囚犯提供数学和科学课程。Krumholtz博士将与加州大学圣克鲁斯分校的教职员工和学生一起参与这项活动，从而促进科学界与基本得不到服务的少数民族之间的互动。

While there has been considerable progress toward the development of a standard model for the process of star formation in the case of low mass stars, we are much further from understanding how massive stars form. Massive stars produce most of the metals in the universe, dominate the energy balance of both the interstellar and intergalactic media via their ionizing radiation, winds, and supernovae, and shape the formation of planets through their interactions with nearby protoplanetary disks. No understanding of these processes is possible without a reliable model of massive star formation. In this project, Dr. Mark Krumholz (University of California - Santa Cruz) will develop such a model, using the complementary tools of analytic investigation and high resolution simulation including gravity, radiation, and magnetohydrodynamics.As part of this research a number of questions and problems must be addressed. At the earliest stages of massive star formation, we must understand the fragmentation process. What physical mechanisms control whether gas fragments down to sizes less than one solar mass or collapses monolithically to a massive star? Once collapse begins, any model must describe how to overcome the two dominant barriers to accretion, angular momentum and radiation pressure. Disks are a likely solution, since they redistribute angular momentum while at the same time their high opacity shields gas from radiation. A second important part of this project is to develop an understanding of massive protostellar disks. At the end of the massive star formation process, what eventually halts accretion and clears away any remaining gas? In addition to working on these questions, and using material related to this research, Dr. Krumholtz will also offer math and science courses to prison inmates in prisons near Santa Cruz, California, building on Dr. Krumholz's decade of experience in prison education. Dr. Krumholtz will involve faculty, staff, and students at UC Santa Cruz in this activity, thereby facilitating interactions between the scientific community and a radically under-served, largely minority population.