Synthetic Large-scale Galactic Filaments: On Their Formation, Physical Properties, and Resemblance to Observations
Synthetic Large-scale Galactic Filaments: On Their Formation, Physical Properties, and Resemblance to Observations
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DOI：
10.3847/1538-4357/ab517d
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发表时间：
2019-10
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影响因子：
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通讯作者：
C. Zucker;Rowan J. Smith;A. Goodman
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作者：
C. Zucker;Rowan J. Smith;A. Goodman
利用从一个类似银河系的星系的AREPO模拟中提取的大尺度细丝，我们试图理解观察到的大尺度细丝特性（长度≥100pc）在多大程度上可以单独用星系动力学来解释。从星系盘的观察者角度来看，我们发现细丝的形成纯粹是由于星系动力学，没有反馈或局部自引力的影响。我们发现大规模的星系细丝本质上是罕见的，我们估计，当从银河系中太阳的方向观察时，每kpc2最多应该在投影中识别出大约一个细丝。在这种理想情况下，我们在臂和臂间区域都发现了细丝，并假设前者可能是由于螺旋势井中的气体压缩，后者是由于差速旋转。使用与先前观测相同的分析管道，我们分析了大规模星系细丝的物理特性，并量化了它们对投影效应和星系环境的敏感性（即，它们是否位于臂区或臂间区）。我们发现观测到的“巨分子细丝”与由星系动力学主导的非自引力结构相一致。更直、更窄、更密集的“骨状”细丝，如典型的尼斯细丝，与我们简单模型中的细丝具有相似的柱密度、速度梯度和银河面高度（z≈0 pc），但必须引用额外的物理效应（如反馈和自重力）来解释它们的长度和宽度。
Using a population of large-scale filaments extracted from an AREPO simulation of a Milky Way–like galaxy, we seek to understand the extent to which observed large-scale filament properties (with lengths ≳100 pc) can be explained by galactic dynamics alone. From an observer’s perspective in the disk of the galaxy, we identify filaments forming purely due to galactic dynamics, without the effects of feedback or local self-gravity. We find that large-scale galactic filaments are intrinsically rare, and we estimate that at maximum approximately one filament per kpc2 should be identified in projection, when viewed from the direction of our Sun in the Milky Way. In this idealized scenario, we find filaments in both the arm and interarm regions and hypothesize that the former may be due to gas compression in the spiral potential wells, with the latter due to differential rotation. Using the same analysis pipeline applied previously to observations, we analyze the physical properties of large-scale galactic filaments and quantify their sensitivity to projection effects and galactic environment (i.e., whether they lie in the arm or interarm regions). We find that observed “Giant Molecular Filaments” are consistent with being non-self-gravitating structures dominated by galactic dynamics. Straighter, narrower, and denser “Bone-like” filaments, like the paradigmatic Nessie filament, have similar column densities, velocity gradients, and galactic plane heights (z ≈ 0 pc) to those in our simple model, but additional physical effects (such as feedback and self-gravity) must be invoked to explain their lengths and widths.