论文标题
分离光谱数据中速度和密度贡献的技术及其在研究湍流和磁场上的应用
Technique for separating velocity and density contributions in spectroscopic data and its application to studying turbulence and magnetic fields
论文作者
论文摘要
基于Lazarian＆Pogosyan（2000）中位置位置速度（PPV）统计的理论描述，我们在分离出速度和密度波动引起的PPV波动时引入了一种称为速度分解算法（VDA）的新技术。使用MHD湍流模拟，我们证明了其在各种物理条件下从PPV立方体检索速度波动及其准确追踪磁场的前景的希望。我们发现，对于局部云，速度波动在光谱线的机翼部分最突出，它们主导着密度波动。相同的速度优势适用于经历银河旋转的延长的HI区域。我们的数值实验表明，由原子氢（HI）冷阶段引起的速度通道仍会受到小尺度下速度波动的影响。我们将VDA应用于与高速云HVC186+19-114和High Latitude Galactic diffuse HI数据相对应的HI GALFA-DR2数据。我们的研究证实了速度波动在解释为什么在PPV立方体中观察到线性结构的关键作用。我们讨论了VDA对磁场研究的含义和预测极化银河发射，这是宇宙微波背景研究的前景。此外，我们解决了与HI通道图的丝状性质相关的争议，并解释了速度波动在PPV数据立方体中结构形成中的重要性。 VDA将允许天文学家从几乎所有光谱PPV数据中获得速度波动，并允许在观测中直接研究湍流速度场。
Based on the theoretical description of Position-Position-Velocity(PPV) statistics in Lazarian & Pogosyan(2000), we introduce a new technique called the Velocity Decomposition Algorithm(VDA) in separating the PPV fluctuations arising from velocity and density fluctuations. Using MHD turbulence simulations, we demonstrate its promise in retrieving the velocity fluctuations from PPV cube in various physical conditions and its prospects in accurately tracing the magnetic field. We find that for localized clouds, the velocity fluctuations are most prominent at the wing part of the spectral line, and they dominate the density fluctuations. The same velocity dominance applies to extended HI regions undergoing galactic rotation. Our numerical experiment demonstrates that velocity channels arising from the cold phase of atomic hydrogen (HI) are still affected by velocity fluctuations at small scales. We apply the VDA to HI GALFA-DR2 data corresponding to the high-velocity cloud HVC186+19-114 and high latitude galactic diffuse HI data. Our study confirms the crucial role of velocity fluctuations in explaining why linear structures are observed within PPV cubes. We discuss the implications of VDA for both magnetic field studies and predicting polarized galactic emission that acts as the foreground for the Cosmic Microwave Background studies. Additionally, we address the controversy related to the filamentary nature of the HI channel maps and explain the importance of velocity fluctuations in the formation of structures in PPV data cubes. VDA will allow astronomers to obtain velocity fluctuations from almost every piece of spectroscopic PPV data and allow direct investigations of the turbulent velocity field in observations.
