Star Formation: Following the Evolutionary Sequence from Cloud Assembly through Protostars and Circumstellar Disks

恒星形成：遵循从云聚集到原恒星和星周盘的演化序列

• 批准号: RGPIN-2015-04208
• 负责人: Johnstone, Douglas
• 金额: $ 2.04万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=612833
• 关键词: Star; Formation; Following; Evolutionary; Sequence

The bulk of the star formation in our Galaxy takes place within giant molecular clouds. At its simplest, the formation of a star is the result of localized gravitational collapse and the properties of the resulting star-disk system are dependent on the amount and distribution of the gas reservoir, along with its kinematics and angular momentum. Observations of molecular clouds, however, reveal a dynamic environment with large-scale supersonic flows, significant shear, and evidence for supersonic turbulence. The denser gases within the clouds, which correlate with the locations of on-going star formation, show a more ordered structure, beginning with a network of filaments housing dense clumps and cores. Some of these filaments may denote shock front interfaces and others may relate directly to the gravitational infall within the cloud. Indeed, it is expected that the formation of structure within a molecular cloud is due to the competition between gravity and large-scale supersonic (turbulent) motion. Magnetic field mediation may also play an important role. This Discovery Grant will enable research on the flow of mass, energy, and momentum through molecular clouds and over time. In order to determine the end-state - a young star with a planetary system - it is necessary to understand how mass and angular momentum funnel down from the dense natal cloud core. This dense cloud core must be investigated in relationship to the larger molecular cloud, and especially to the network of internal filamentary structure. Finally, the morphology and kinematics within the cloud, including the filamentary structure, relate to the formation and evolution of the molecular cloud itself. To complicate matters, several feedback loops must be taken into account, most critically the energy and momentum of jets and winds from the forming stars themselves.  My graduate student team will investigate the importance of supersonic (turbulent) shocks through observations of excited carbon monoxide, following theoretical calculations of the expected energy dissipation rate. We will continue to actively investigate dense gas structures within clouds through: theoretical work on the modes of star formation; observational determinations of gravitational stability in pre-stellar cores; and comparison of the observed stability range and evolutionary state of cores against simulations. Additionally, we will champion direct investigations into the possibility of proto-star mass assembly via episodic bursts, through ALMA observations.  This Discovery Grant will enable my team to continue its leadership role in the field of star formation, taking advantage of the recent large surveys of molecular clouds (JCMT, Herschel, Spitzer), the unprecedented sensitivity and angular resolution of new instrumentation (ALMA, JWST), and the level of detail available in current and anticipated numerical simulations.

我们银河系中大部分星星的形成都发生在巨大的分子云中。最简单地说，星星的形成是局部引力坍缩的结果，所产生的星盘系统的性质取决于气体储存的数量和分布，沿着其运动学和角动量。然而，对分子云的观测揭示了一个动态环境，其中有大尺度的超音速流、显著的切变和超音速湍流的证据。云内密度较大的气体与正在形成的星星的位置有关，它们呈现出更有序的结构，从一个包含密集团块和核心的细丝网络开始。这些细丝中的一些可能表示激波前缘界面，而其他细丝可能直接与云内的重力下降有关。事实上，人们预期分子云内部结构的形成是由于重力和大尺度超音速（湍流）运动之间的竞争。磁场调解也可能发挥重要作用。这项发现补助金将使研究的质量，能量和动量的流动，通过分子云和随着时间的推移。 为了确定最终状态--一颗拥有行星系统的年轻星星--有必要了解质量和角动量是如何从致密的纳塔尔云核心向下漏斗的。这个稠密的云核必须与更大的分子云，特别是内部的网状结构联系起来研究。最后，分子云内部的形态学和运动学，包括对流结构，与分子云本身的形成和演化有关。使问题复杂化的是，必须考虑到几个反馈回路，最关键的是来自形成中的恒星本身的喷流和风的能量和动量。 我的研究生团队将通过对激发的一氧化碳的观测，以及对预期能量耗散率的理论计算，来研究超音速（湍流）激波的重要性。我们将继续积极研究云内的致密气体结构，通过：星星形成模式的理论工作;观测确定星前核心的引力稳定性;以及将观测到的稳定范围和核心的演化状态与模拟进行比较。此外，我们将通过阿尔马观测，支持对原恒星质量组装通过偶发爆发的可能性进行直接调查。 这一发现补助金将使我的团队能够继续在星星形成领域发挥领导作用，利用最近的分子云大型调查（JCMT，Herschel，Spitzer），新仪器（阿尔马，JWST）前所未有的灵敏度和角分辨率，以及当前和预期的数值模拟的详细程度。