标题： 星际湍流的间歇性：强烈速度剪切的秒差距尺度相干结构 显示英文标题

标题： Intermittency of interstellar turbulence: Parsec-scale coherent structure of intense velocity-shear

摘要： 基于湍流的二元性（随机与相干），我们在分子云的湍流速度场中寻找相干结构，预期它们在云演化中的重要性。 我们分析了一张大范围的图（40'乘20'），该图使用HERA多波束接收器（IRAM-30m望远镜）在北极星翼区的一个高纬度云中获得，在12CO(2-1)线中实现了前所未有的空间（11"）和光谱（0.05 km/s）分辨率。 我们发现两个相差约2 km/s的秒差距尺度的速度组分共享一个狭窄的界面（$<0.15$pc），该界面表现为强烈的速度剪切的延伸结构，约为15至30 km/s/pc。 该场中线-中心速度增量（E-CVI）极值的轨迹也遵循这种强剪切结构以及12CO(2-1)高速度线翼的轨迹。 这两个秒差距尺度组分在投影上的微小空间重叠表明，它们是CO发射的片状结构，并且在强烈速度剪切的位置出现气体性质（CO富集和/或气体密度增加）的不连续性。 这些结果揭示了从0.03 pc小尺度到秒差距尺度之间的空间和运动学相干性。 它们证实了E-CVI概率密度函数的非高斯性是湍流间歇性的强大统计示踪工具。 它们揭示了大尺度湍流、其间歇性耗散率与低质量致密核心形成之间的联系。 显示英文摘要

摘要： Guided by the duality of turbulence (random versus coherent we seek coherent structures in the turbulent velocity field of molecular clouds, anticipating their importance in cloud evolution. We analyse a large map (40' by 20') obtained with the HERA multibeam receiver (IRAM-30m telescope) in a high latitude cloud of the Polaris Flare at an unprecedented spatial (11") and spectral (0.05 km/s) resolutions in the 12CO(2-1) line. We find that two parsec-scale components of velocities differing by ~2 km/s, share a narrow interface ($<0.15$ pc) that appears as an elongated structure of intense velocity-shear, ~15 to 30 km/s/pc. The locus of the extrema of line--centroid-velocity increments (E-CVI) in that field follows this intense-shear structure as well as that of the 12CO(2-1) high-velocity line wings. The tiny spatial overlap in projection of the two parsec-scale components implies that they are sheets of CO emission and that discontinuities in the gas properties (CO enrichment and/or increase of gas density) occur at the position of the intense velocity shear. These results disclose spatial and kinematic coherence between scales as small as 0.03 pc and parsec scales. They confirm that the departure from Gaussianity of the probability density functions of E-CVIs is a powerful statistical tracer of the intermittency of turbulence. They disclose a link between large scale turbulence, its intermittent dissipation rate and low-mass dense core formation.