论文标题
观察到的H I细丝湍流或密度结构吗？速度苛刻，事实和假货
Are observed H i filaments turbulent illusions or density structures? Velocity caustics, facts and fakes
论文作者
论文摘要
语境。星际培养基受湍流的影响，并且在通道图中观察到的H I结构受湍流运动的形状。几个理论家认为，观察到的H I结构并不代表实际密度增强，而是由速度拥挤引起的速度苛刻。克拉克等人对这种解释进行了质疑。导致暴力辩论。目标。为了解决讨论，我们通过使用Effelsberg Bonn H I调查（EBHIS）观察来验证理论关键参数。方法。我们应用UNSHARP屏蔽以在高空间频率下确定丝状H I结构。此外，我们使用高斯参数将冷中性培养基（CNM）与观察到的H I色谱柱密度区分开。我们比较灰尘和H I色谱柱密度的功率谱和空间分布，从而区分各种速度宽度的CNM和多相密度。结果。观察结果与速度通道分析（VCA）相矛盾，假设频谱指数应随速度窗口的宽度而陡峭。我们宁愿发现，薄片光谱指数在很大程度上取决于H I相组成。多相功率谱对于冷气区域更陡峭。 VCA否认这种相位依赖性对电源分布的依赖性。分开CNM，我们发现功率谱比多相H I复合材料的功率光谱明显更平整。我们观察到源自CNM中的冷尘轴承细丝的小规模结构的CNM功率过多。狭窄通道宽度的光谱指数取决于H I气体的多普勒温度。在有增强的小规模H I结构的情况下，灰尘的远红外发射也将增强。结论。小规模的冷丝状H I结构主要是由于相变而不是速度苛性速度引起的密度增强引起的。
Context. The interstellar medium is affected by turbulence and observed H i structures in channel maps are shaped by turbulent motions. It is taken for granted by a few theoreticians that observed H i structures do not represent real density enhancement but velocity caustics, caused by velocity crowding. This interpretation was questioned and objections by Clark et al. led to violent debates. Aims. To settle the discussion we verify theoretical key parameters by using Effelsberg Bonn H i Survey (EBHIS) observations. Methods. We apply unsharp masking to determine filamentary H i structures at high spatial frequencies. In addition we use Gaussian parameters to distinguish the cold neutral medium (CNM) from observed H i column densities. We compare power spectra and spatial distributions of dust and H i column densities, distinguishing CNM and multiphase column densities at various velocity widths. Results. Observations contradict the Velocity Channel Analysis (VCA) postulate that the spectral index should steepen with the width of the velocity window. We rather find that the thin slice spectral index depends strongly on the H i phase composition. Multiphase power spectra are steeper for regions with cold gas. VCA denies such H i phase dependencies on the power distribution. Separating the CNM we find that the power spectra are significantly flatter than those for the multiphase H i composite. We observe excess CNM power for small scale structures originating from cold dust bearing filaments that are embedded in the CNM. Spectral indices for narrow channel widths depend on the Doppler temperature of the H i gas. In presence of enhanced small scale H i structure the far infrared emission from dust is also enhanced. Conclusions. Small scale cold filamentary H i structures are predominantly caused by density enhancements due to phase transitions rather than by velocity caustics.
