论文标题
尘埃在分子云形成中的动态作用
Dynamic role of dust in formation of molecular clouds
论文作者
论文摘要
灰尘是星际介质的通常次要组成部分。由于质量分数很小，$ f \ simeq 0.01 $，通常认为它在弥漫性气体在分子云中的收缩中的动态作用被认为可以忽略不计。但是，如本研究所示，相对于气体的集体运动可能会大大导致介质对尺度上的稳定，$λ\ simsimλ_j$，其中$λ_j$是牛仔裤的长度规模。 The linear perturbations of the uniform self-gravitating gas at rest are marginally stable at $λ\simeq λ_J$, but as soon as the drift of grains is taken into account, they begin growing at a rate approximately equal to $(f τ)^{1/3} t^{-1}_{ff}$, where $τ$ is the stopping time of grains expressed in units of the free fall云的时间，$ t_ {ff} $。导致生长速率如此微弱依赖性$ f $的物理机制是，沉重的声波的共鸣是由于气体的自我重力所阻止的，由于灰尘分数的扰动而引起的引力较弱的吸引力。一旦存在固定的亚音速散装漂移，$λ<λ_j$以$λ<λ_j$的生长气盘扰动将随着投影到波形向量的漂移速度而传播的波。它们的生长也具有共鸣的性质，并且在没有自我重力的情况下，增长率大大比最近发现的气盘混合物共振不稳定性的增长率要大得多。新的不稳定性可以促进冷星气体的重力收缩到云层中，并在分子云形成和进化的不同阶段产生亚jeans大小的灰尘域。
Dust is the usual minor component of the interstellar medium. Its dynamic role in the contraction of the diffuse gas into molecular clouds is commonly assumed to be negligible because of the small mass fraction, $f \simeq 0.01$. However, as shown in this study, the collective motion of dust grains with respect to the gas may considerably contribute to the destabilisation of the medium on scales $λ\lesssim λ_J$, where $λ_J$ is the Jeans length-scale. The linear perturbations of the uniform self-gravitating gas at rest are marginally stable at $λ\simeq λ_J$, but as soon as the drift of grains is taken into account, they begin growing at a rate approximately equal to $(f τ)^{1/3} t^{-1}_{ff}$, where $τ$ is the stopping time of grains expressed in units of the free fall time of the cloud, $t_{ff}$. The physical mechanism responsible for such a weak dependence of the growth rate on $f$ is the resonance of heavy sound waves stopped by the self-gravity of gas with weak gravitational attraction caused by perturbations of the dust fraction. Once there is stationary subsonic bulk drift of the dust, the growing gas-dust perturbations at $λ< λ_J$ become waves propagating with the drift velocity projected onto the wavevector. Their growth has a resonant nature as well and the growth rate is substantially larger than that of the recently discovered resonant instability of gas-dust mixture in the absence of self-gravity. The new instabilities can facilitate gravitational contraction of cold interstellar gas into clouds and additionally produce dusty domains of sub-Jeans size at different stages of molecular cloud formation and evolution.
