论文标题
模拟湍流云的合成线和连续观测：细丝的明显宽度
Synthetic line and continuum observations of simulated turbulent clouds: the apparent widths of filaments
论文作者
论文摘要
丝状结构无处不在，在对真实分子云的观察中，以及湍流，自我散热气体的模拟中。但是，对观察和模拟之间的比较是由于在观察上估算体积浓度的困难而变得复杂。在这里，我们使用了全日制依赖化学网络对湍流等温分子云进行后处理的流体动力学模拟。然后，我们运行了辐射转移模型，以获得可以直接将其与观察到的合成线和连续强度进行比较。我们发现，丝具有$ \，\ sim \！0.1 \，{\ rm pc} $的特征宽度，既在其真实的表面密度的地图上，又在其$ 850 \，{\rmμm} $ dust-dofle-dust-dost-continuum发射的地图上，与先前的工作一致。在来自CO同位素学的线发射图上，细丝的明显宽度通常大几倍，因为线强度与表面密度的相关性很差。在诸如n $ _2 $ h $^+$和HCN等密集的气体示踪剂的线排放图上，丝的明显宽度为$ \ sillesim 0.1 \，{\ rm pc} $。因此，目前对分子线排放的观察结果与通用$ 0.1 \，{\ rm pc} $丝宽宽度兼容，从$ {\ it herschel} $观测中推断出，前提是适当的帐户是有丰度，光学深度和激励考虑的。我们发现$ \ sim 0.4 \，{\ rm km \，s^{ - 1}} $ radial速度差异之间的证据。这些径向速度差异可能是灯丝形成或正在形成的机制的有用指标，例如在此建模的湍流云方案，而不是其他机制，例如云云碰撞。
Filamentary structures are ubiquitous in observations of real molecular clouds, and also in simulations of turbulent, self-gravitating gas. However, making comparisons between observations and simulations is complicated by the difficulty of estimating volume-densities observationally. Here, we have post-processed hydrodynamical simulations of a turbulent isothermal molecular cloud, using a full time-dependent chemical network. We have then run radiative transfer models to obtain synthetic line and continuum intensities that can be compared directly with those observed. We find that filaments have a characteristic width of $\,\sim\!0.1 \, {\rm pc}$, both on maps of their true surface density, and on maps of their $850 \, {\rm μm}$ dust-continuum emission, in agreement with previous work. On maps of line emission from CO isotopologues, the apparent widths of filaments are typically several times larger because the line intensities are poorly correlated with the surface density. On maps of line emission from dense-gas tracers such as N$_2$H$^+$ and HCN, the apparent widths of filaments are $\lesssim 0.1 \, {\rm pc}$. Thus, current observations of molecular-line emission are compatible with the universal $0.1 \, {\rm pc}$ filament width inferred from ${\it Herschel}$ observations, provided proper account is taken of abundance, optical-depth, and excitation considerations. We find evidence for $\sim 0.4 \, {\rm km \, s^{-1}}$ radial velocity differences across filaments. These radial velocity differences might be a useful indicator of the mechanism by which a filament has formed or is forming, for example the turbulent cloud scenario modelled here, as against other mechanisms such as cloud-cloud collisions.
