Virial Clumps in Central Molecular Zone Clouds
Virial Clumps in Central Molecular Zone Clouds
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DOI：
10.3847/1538-4357/ac5906
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发表时间：
2022-02
期刊：
影响因子：
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通讯作者：
P. Myers;H. P. Hatchfield;C. Battersby
中科院分区：
文献类型：
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作者：
P. Myers;H. P. Hatchfield;C. Battersby
为了描述银河系中央分子带(CMZ)22个星云中755个星团的维里平衡(VE)和恒星形成势，对亚毫米阵列的CMZoom观测数据进行了分析。在每个云中，几乎所有的团块都遵循柱状密度-质量趋势N∝M S，其中S=0.38±0.03在压界极限S p=1/3附近。当VE中的重力非结合团块具有相似的速度弥散和外部压力时，这种趋势是预期的。这些云团中有九个还隐藏着一个或两个明显更大的团块。这些属性允许在每个云中建立绑定和未绑定块的VE模型，其中最大质量的块具有VE临界质量。这些模式表明，2 13个星团具有速度弥散1-2公里S−1，平均外压(0.5-4)×10~8 cm−3K，结合星团分数0.0 6，典型维里参数α=4-15。这些大部分非结合星团可能处于VE中，它们的湍流云压力可能是由来自银河的流入所驱动。相反，大多数SGR B2簇是根据其相关的来源和N-M趋势而绑定的。当CMZ团块组合成质量分布时，用停止吸积模型分析了其典型的幂函数斜率。它还表明，大多数团块是无结合的，不能显著生长，因为它们的吸积和扩散时间相似，∼为0.2Myr。因此，对现有的最广泛的星团普查进行的维里和动力学分析表明，CMZ中恒星的形成可能受到重力束缚星团的显著不足的抑制。
CMZoom survey observations with the Submillimeter Array are analyzed to describe the virial equilibrium (VE) and star-forming potential of 755 clumps in 22 clouds in the Central Molecular Zone (CMZ) of the Milky Way. In each cloud, nearly all clumps follow the column density–mass trend N ∝ M s , where s = 0.38 ± 0.03 is near the pressure-bounded limit s p = 1/3. This trend is expected when gravitationally unbound clumps in VE have similar velocity dispersion and external pressure. Nine of these clouds also harbor one or two distinctly more massive clumps. These properties allow a VE model of bound and unbound clumps in each cloud, where the most massive clump has the VE critical mass. These models indicate that 213 clumps have velocity dispersion 1–2 km s−1, mean external pressure (0.5–4) × 108 cm−3 K, bound clump fraction 0.06, and typical virial parameter α = 4–15. These mostly unbound clumps may be in VE with their turbulent cloud pressure, possibly driven by inflow from the Galactic bar. In contrast, most Sgr B2 clumps are bound according to their associated sources and N–M trends. When the CMZ clumps are combined into mass distributions, their typical power-law slope is analyzed with a model of stopped accretion. It also indicates that most clumps are unbound and cannot grow significantly, due to their similar timescales of accretion and dispersal, ∼0.2 Myr. Thus, virial and dynamical analyses of the most extensive clump census available indicate that star formation in the CMZ may be suppressed by a significant deficit of gravitationally bound clumps.