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: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=685500
• 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. **** **

恒星的形成发生在分子云中最稠密的气体中，而行星则由原恒星周围更稠密的气体形成。 在这个提案中，我描述了利用最新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、团块和圆盘。  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监督下的学生进行。****赫歇尔太空天文台最近透露，云中的大量质量以细丝形式存在，最密集的例子是致密气体袋的主要位置，即致密核心和原恒星。   这些数据表明细丝在恒星形成过程中的关键作用，即提供恒星形成最有效的条件。  因此，了解它们的起源很重要，并且可以通过其运动学的进一步数据进行探索。 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丝状区域的一些令人信服的数据，但我建议使用来自詹姆斯·克拉克·麦克斯韦望远镜 (JCMT) 古尔德带巡天的 CO、13CO 和 C18O 线数据来探测各种丝状体的运动学，并通过模型比较确定它们的动力学状态和起源。****赫歇尔还揭示了丝状体可能与恒星的形成有关。 在细丝的交叉点处发现了团簇，即比核心质量更大的致密气体袋，它们可能分裂成紧密的核心组合，即团块。  这种布置为簇形成提供了一种优雅的解决方案，因为增加的质量流途径可用于将特定区域增长到高密度。  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，细丝的交叉点是否是物理连接？  我建议使用美国国家射电天文台的绿岸望远镜 (GBT) 和詹斯基甚大阵列 (JVLA) 来观察附近云中细丝交叉的 NH3 线发射，特别是那些几乎没有恒星形成的云，并评估它们的运动学。***最后，我建议解决行星形成的原恒星附近扁平结构的形成问题， 即磁盘。  对圆盘最早时期的观测将了解圆盘演化的初始条件以及任何随后的行星形成。 然而，赫歇尔和 JCMT 不具备探测此类结构的角分辨率。  相反，我建议使用来自新阿塔卡马大型毫米波阵列 (ALMA) 的连续谱和（N2H+ 和 H2D+）线数据来研究处于恒星形成事件边缘或刚刚超出恒星形成事件的核心中心的致密气体的密度和速度。 ** **