论文标题
为什么大多数分子云在重力上占主导地位
Why most molecular clouds are gravitationally dominated
论文作者
论文摘要
观察和理论证据表明，大量的分子云（MC）似乎是未结合的，以湍流运动为主。但是，这些估计通常是通过所谓的病毒参数$α_ {\ rm vir}^{\ rm class} $进行的，这是动力学和重力能量之间的病毒比率的观察性代理。该参数本质地假设MC是孤立的，球形的，并且具有恒定密度。但是，MC嵌入了其母星系中，因此受到星系中的压缩和破坏性的潮汐力，表现出不规则的形状，并显示出大量的子结构。因此，我们将$α_ {\ rm vir}^{\ rm class} $的典型估计与病毒参数的更精确定义，$α_ {\ rm vir}^{\ rm full} $，不仅用于自我gravity（$ a} $ n vir，rm rmm rm rm rm rm rm rm rm rm rm rm rm rm rm {潮汐应力，因此，它可以承受负（自我重力）和正（潮汐）值。 While we recover the classical result that most of the clouds appear to be unbound, having $α_{\rm vir}^{\rm class} > 2$, we show that, with the more detailed definition considering the full gravitational energy, (i) 50\%\ of the total population is gravitationally bound, however, (ii) another 20\%\ is gravitationally dominated, but with tides tearing them apart; （iii）这些潮汐的来源不是来自银河系结构（凸起，光晕，螺旋臂），而是来自云的分子云配合物，如果存在云的云层，则可能来自大型的年轻恒星复合物（IV）。 （v）最后，我们的结果还表明，星际湍流至少可以部分地具有引力起源。
Observational and theoretical evidence suggests that a substantial population of molecular clouds (MCs) appear to be unbound, dominated by turbulent motions. However, these estimations are made typically via the so-called viral parameter $α_{\rm vir}^{\rm class}$, which is an observational proxy to the virial ratio between the kinetic and the gravitational energy. This parameter intrinsically assumes that MCs are isolated, spherical, and with constant density. However, MCs are embedded in their parent galaxy and thus are subject to compressive and disruptive tidal forces from their galaxy, exhibit irregular shapes, and show substantial substructure. We, therefore, compare the typical estimations of $α_{\rm vir}^{\rm class}$ to a more precise definition of the virial parameter, $α_{\rm vir}^{\rm full}$, which accounts not only for the self-gravity (as $α_{\rm vir}^{\rm class}$), but also for the tidal stresses, and thus, it can take negative (self-gravity) and positive (tides) values. While we recover the classical result that most of the clouds appear to be unbound, having $α_{\rm vir}^{\rm class} > 2$, we show that, with the more detailed definition considering the full gravitational energy, (i) 50\%\ of the total population is gravitationally bound, however, (ii) another 20\%\ is gravitationally dominated, but with tides tearing them apart; (iii) the source of those tides does not come from the galactic structure (bulge, halo, spiral arms), but from the molecular cloud complexes in which clouds reside, and probably (iv) from massive young stellar complexes, if they were present. (v) Finally, our results also suggest that, interstellar turbulence can have, at least partially, a gravitational origin.
