Filaments, Clumps, and Disks: Investigating the Origins of Star- and Planet-Forming Structures in Molecular Clouds

细丝、团块和圆盘：研究分子云中恒星和行星形成结构的起源

• 批准号: RGPIN-2015-05308
• 负责人: DiFrancesco, James
• 金额: $ 2.55万
• 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=613473
• 关键词: Filaments; Clumps; Disks; Investigating; Origins

Star formation occurs within the densest gas of molecular clouds and planets form out of even denser gas surrounding protostars. In this proposal, I describe plans to exploit the newest observational technologies to determine the origins of substructure in molecular clouds that promote the formation of stars and planets, i.e., filaments, clumps, and disks.  With these projects, Canada will continue its leading role in probing the origins of stars and planets.  These projects will also be undertaken primarily by students under my direct supervision. The Herschel Space Observatory recently revealed that significant mass in clouds is found in filaments, with the densest examples being the predominant locations of compact pockets of gas, i.e., dense cores, and protostars.   These data indicate the pivotal role of filaments in the star formation process, i.e, providing the conditions from which star formation is most efficient.  Understanding their origins is therefore important, and can be explored with further data of their kinematics. For example, are filaments equilibrium or non-equilibrium structures?  Though some compelling data of a few filamentary regions have been obtained, I propose to use line data of CO, 13CO, and C18O from the James Clerk Maxwell Telescope (JCMT) Gould Belt Survey to probe the kinematics of a wide variety of filaments and through model comparisons determine their dynamical states and origins. Herschel also revealed that filaments may be implicated in the formation of stellar clusters, as compact pockets of gas more massive than cores that may fragment into tight associations of cores, i.e., clumps, are found at the intersections of filaments.  This arrangement provides an elegant solution to cluster formation, as increased avenues of mass flow are available to grow a specific region to high densities.  Nevertheless, the kinematics of filaments associated with clumps require investigation to determine if this scenario is realistic, e.g., are intersections physical connections of filaments?  I propose to use the U.S. National Radio Astronomy Observatory's Green Bank Telescope (GBT) and Jansky Very Large Array (JVLA) to observe NH3 line emission towards such examples of filament intersection in nearby clouds, specifically those with little to no star formation, and assess their kinematics. Finally, I propose to address the formation of the flattened structures near protostars from which planets form, i.e., disks.  Observations of disks at their earliest epochs will inform the initial conditions of disk evolution and any subsequent planet formation. Herschel and JCMT, however, do not have the angular resolution to probe such structures.  Instead, I propose to use continuum and (N2H+ and H2D+) line data from the new Atacama Large Millimeter Array (ALMA) to investigate the densities and velocities of dense gas in the centers of cores on the verge or just beyond the star formation event.

星星的形成发生在分子云的致密气体中，而行星则是由原恒星周围更致密的气体形成的。在这个建议中，我描述了利用最新的观测技术来确定分子云中促进恒星和行星形成的子结构起源的计划，即，细丝、团块和盘。通过这些项目，加拿大将继续在探索恒星和行星的起源方面发挥主导作用。这些项目也将主要由我直接指导的学生承担。 赫歇尔空间天文台最近发现，云中的大量物质存在于细丝中，致密的例子是致密气体的主要位置，即，致密的核心和原恒星 这些数据表明暗条在星星形成过程中的关键作用，也就是说，暗条提供了星星形成最有效的条件。因此，了解暗条的起源很重要，可以通过进一步的运动学数据来探索。例如，细丝是平衡结构还是非平衡结构？ 虽然已经获得了一些令人信服的数据的一些附属区域，我建议使用线数据的CO，13 CO，和C18 O的詹姆斯克拉克麦克斯韦望远镜（JCMT）古尔德带调查，以探测各种各样的细丝的运动学，并通过模型比较确定其动力学状态和起源。 赫歇尔还揭示了细丝可能与恒星团的形成有关，因为致密的气体袋比核心更重，可能会分裂成紧密的核心关联，即，在细丝的交叉处发现了团块。这种排列提供了一种优雅的解决方案来形成集群，因为增加的质量流途径可以使特定区域生长到高密度。然而，与团块相关的细丝的运动学需要调查以确定这种情况是否现实，例如，交叉点是细丝的物理连接吗？ 我建议使用美国国家射电天文台的绿色银行望远镜（GBT）和Jansky甚大阵（JVLA）观察NH3线发射对这样的例子灯丝交叉在附近的云，特别是那些很少或没有星星形成，并评估其运动学。 最后，我建议解决形成行星的原恒星附近的扁平结构的形成，即，在最早期对盘的观测将为盘演化和任何随后的行星形成提供信息。然而，Herschel和JCMT没有探测这种结构的角分辨率，相反，我建议使用新的阿塔卡马大毫米阵列（阿尔马）的连续谱和（N2H+和H2D+）线数据来研究星星形成事件边缘或附近核心中致密气体的密度和速度。