论文标题
模拟冷HI结构的物理和几何特性
The physical and the geometrical properties of simulated cold HI structures
论文作者
论文摘要
本文的目的是帮助阐明通过磁化原子星际培养基中热不稳定性形成的冷结构的性质和特性。为此，我们搜索了在强制（磁铁）流体动力模拟中形成的团块，初始磁场范围从0到8.3 $μg。我们通过使用核密度估计，统计分析了包含$ \ sim 1500 $团块的样品的物理和形态特性，以及团块的主要方向与内部速度和磁场之间的相对一致性。密度（$ n \ sim 50-200 $ cm $^{ - 3} $），热压（$ p_ {th}/k \ sim 4.9 \ sim 4.9 \ times 10^3-10^4 $ k cm $^{ - 3} $），平均磁场（$ \ sim 3-11 $ $ g），以及对这些选择的clbosection complose comploce comport comports comports compoct compoct comport consonic clansoct consonic mach norks clump cllump clump clump clump clump。但是，我们发现云样本无法通过单个制度来描述其压力平衡和其Alfénic马赫数。我们主要通过非球面和延长度测量了团块的形态特性，这似乎比长宽比更敏感。从该分析中，我们发现磁场的存在，即使它很弱，也确实通过将高度非小质和高度倾斜的团块增加了两个因素而定性地影响了团块的形态，这是通过产生更多的丝状团块。最后，我们发现团块的主要方向与局部磁场之间的角度位于$ \simπ/4-π/2 $之间，并且随着该场的强度的增加而转移到更垂直的比对，而局部密度结构与局部磁场之间的相对方向从平行到垂直于垂直。
The objective of this paper is to help shedding some light on the nature and the properties of the cold structures formed via thermal instability in the magnetized atomic interstellar medium. To this end, we searched for clumps formed in forced (magneto)hydrodynamic simulations with an initial magnetic field ranging from 0 to 8.3$μ$G. We statistically analyzed, through the use of Kernel Density Estimations, the physical and the morphological properties of a sample containing $\sim 1500$ clumps, as well as the relative alignments between the main direction of clumps and the internal velocity and magnetic field. The density ($n\sim 50-200$cm$^{-3}$), the thermal pressure ($P_{th}/k\sim 4.9\times 10^3-10^4$K cm$^{-3}$), the mean magnetic field ($\sim 3-11$$μ$G ), and the sonic Mach number of the selected clumps have values comparable to those reported in observations. We find, however, that the cloud sample can not be described by a single regime concerning their pressure balance and their Alfénic Mach number. We measured the morphological properties of clumps mainly through the asphericity and the prolatness, which appear to be more sensitive than the aspect ratios. From this analysis we find that the presence of magnetic field, even if it is weak, does qualitatively affect the morphology of the clumps by increasing the probability of having highly aspherical and highly plolate clumps by a factor of two, that is by producing more filamentary clumps. Finally, we find that the angle between the main direction of the clumps and the local magnetic field lies between $\simπ/4-π/2$ and shifts to more perpendicular alignments as the intensity of this field increases, while the relative direction between the local density structure and the local magnetic field transits from parallel to perpendicular.
