论文标题
嗨，细丝很冷，与深色分子气体有关。基于HI4PI的局部弥漫性共销H2分布的估计值
HI filaments are cold and associated with dark molecular gas. HI4PI based estimates of the local diffuse CO-dark H2 distribution
论文作者
论文摘要
语境。银河系有大量的H2。由于其对称性，H2不会在无线电频率下辐射。 CO被认为是H2的示踪剂，但是CO在不粘液率明显高于H2的情况下形成。因此，朝向高银河纬度的大量H2被隐藏并称为涂层。目标。我们证明，尘埃气比是识别Co-Dark H2的位置和柱密度的工具。方法。我们采用常数E（B-V）/NH比的假设，与从HI到H2的相变无关。我们研究了多普勒温度TD，从HI4PI数据的高斯分解到研究E（B-V）/NHI的温度依赖性。结果。与温暖的HI气相中的E（B-V）/NHI比相比较高。我们将其视为证据表明，冷的HI气对高银河纬度与H2有关。除了共同区域之外，我们发现TD <1165 K A相关性（NHI + 2NH2）/NHI Prop -log T_D。结合一个因子XCO = 4.0 10 20 cm^-2（k km s^-1）-1这可以使全套NH /E（B-V）SIM 5.1至6.7 10^21 cm^-2 mag^-1组合，与X射线散射和UV吸收线观测值兼容。结论。冷HI，T_D <1165 K平均包含46％的涂层H2。突出的细丝的TD <220 K，典型的激发温度Tex Sim 50 K.分子气体分数> 61％，它们由H2动态主导。
Context. There are significant amounts of H2 in the Milky Way. Due to its symmetry H2 does not radiate at radio frequencies. CO is thought to be a tracer for H2, however CO is formed at significantly higher opacities than H2. Thus, toward high Galactic latitudes significant amounts of H2 are hidden and called CO-dark. Aims. We demonstrate that the dust-to-gas ratio is a tool to identify locations and column densities of CO-dark H2. Methods. We adopt the hypothesis of a constant E(B-V)/NH ratio, independent of phase transitions from HI to H2. We investigate the Doppler temperatures TD, from a Gaussian decomposition of HI4PI data, to study temperature dependencies of E(B-V)/NHI. Results. The E(B-V)/NHI ratio in the cold HI gas phase is high in comparison to the warmer one. We consider this as evidence that cold HI gas toward high Galactic latitudes is associated with H2. Beyond CO-bright regions we find for TD < 1165 K a correlation (NHI + 2NH2 )/NHI prop -log T_D. In combination with a factor XCO = 4.0 10 20 cm^-2 (K km s^-1 )-1 this yields for the full-sky NH /E(B-V) sim 5.1 to 6.7 10^21 cm^-2 mag^-1, compatible with X-ray scattering and UV absorption line observations. Conclusions. Cold HI with T_D < 1165 K contains on average 46% CO-dark H2. Prominent filaments have TD < 220 K and typical excitation temperatures Tex sim 50 K. With a molecular gas fraction of > 61% they are dominated dynamically by H2.
