论文标题
由于超音速融合流的耗散，穆斯卡丝中的密集气体形成
Dense gas formation in the Musca filament due to the dissipation of a supersonic converging flow
论文作者
论文摘要
使用Herschel空间望远镜的观察结果表明，大多数恒星形成的气体都是在星际丝中组织的，这一发现得到了对超音速星际介质（ISM）的数值模拟支持的发现，其中密集的丝状结构无处不在。我们旨在通过使用APEX望远镜使用覆盖$^{12} $ CO（4-3），$^{12} $ CO（3-2）和各种CO（2-1）同位素线的观测值来了解这些致密结构的形成。 The observed CO intensities and line ratios cannot be explained by PDR (photodissociation region) emission because of the low ambient far-UV field that is strongly constrained by the non-detections of the [C II] line at 158 $μ$m and the [O I] line at 63 $μ$m, observed with the upGREAT receiver on SOFIA, as well as a weak [C I] 609 $μ$m line detected with顶点。我们建议观察结果与一种场景一致，在这种情况下，电击激发会导致温暖而密集的气体接近穆斯卡丝中最高的柱密度区域。使用冲击模型，我们发现CO观察可以与J型低速冲击激发一致。观察到的CO光谱与动态丝形成模拟的合成观察结果的定性比较表明，与丝吸积冲击的签名良好一致，从而形成了来自聚合流的冷且密集的细丝。因此，发现Musca细丝是致密的分子后震后气体。丝状吸积冲击会消散ISM中融合流的超音速动能，因此可能在冷和致密的丝状结构的演化中起重要作用。
Observations with the Herschel Space Telescope have established that most of the star forming gas is organised in interstellar filaments, a finding that is supported by numerical simulations of the supersonic interstellar medium (ISM) where dense filamentary structures are ubiquitous. We aim to understand the formation of these dense structures by performing observations covering the $^{12}$CO(4-3), $^{12}$CO(3-2), and various CO(2-1) isotopologue lines of the Musca filament, using the APEX telescope. The observed CO intensities and line ratios cannot be explained by PDR (photodissociation region) emission because of the low ambient far-UV field that is strongly constrained by the non-detections of the [C II] line at 158 $μ$m and the [O I] line at 63 $μ$m, observed with the upGREAT receiver on SOFIA, as well as a weak [C I] 609 $μ$m line detected with APEX. We propose that the observations are consistent with a scenario in which shock excitation gives rise to warm and dense gas close to the highest column density regions in the Musca filament. Using shock models, we find that the CO observations can be consistent with excitation by J-type low-velocity shocks. A qualitative comparison of the observed CO spectra with synthetic observations of dynamic filament formation simulations shows a good agreement with the signature of a filament accretion shock that forms a cold and dense filament from a converging flow. The Musca filament is thus found to be dense molecular post-shock gas. Filament accretion shocks that dissipate the supersonic kinetic energy of converging flows in the ISM may thus play a prominent role in the evolution of cold and dense filamentary structures.
