论文标题
探测加利福尼亚分子云的冷深深度：CO与尘埃之间的冰冷关系
Probing the Cold Deep Depths of the California Molecular Cloud: The Icy Relationship between CO and Dust
论文作者
论文摘要
我们研究了加利福尼亚分子云中的分子气与粉尘之间在空前的云深度范围内（AV = 3-60个幅度）之间的关系。我们将基于HERSCHEL的灰尘灭绝的深度测量与对12CO，13CO和C18O J = 2-1线的观测值进行了比较。我们直接测量了CO集成强度与尘埃灭绝的比率，以在云中超过1E5独立的位置在超过1E5的独立位置得出CO X因子的比率。确认了一项较早的研究，我们发现没有一个12CO X因子可以表征云中云的寒冷（Tdust <20k）区域中分子气体的大部分质量。我们能够在温暖（TDUST> 25 K）材料中为所有三个CO同位素分子得出一个单值X因子，该材料与STAR LKHA101周围的HII区域在空间上是一致的。由于我们发现两条线相对较薄，因此我们得出了13CO和C18O的LTE CO柱密度。在温暖的云材料中，CO完全处于气相，我们能够恢复总的13CO和C18O丰度。使用CO丰度和深度HERSCHEL观察，我们测量了CO将CO冻结到整个云上的灰尘的下限，发现某些区域的CO耗尽了> 20倍。我们构建了跨越巨大分子云范围的第一个耗竭地图。使用这些地图，我们识别75个耗尽定义的核心并讨论其物理性质。
We study the relationship between molecular gas and dust in the California Molecular Cloud over an unprecedented dynamic range of cloud depth (Av = 3 - 60 magnitudes). We compare deep Herschel-based measurements of dust extinction with observations of the 12CO, 13CO, and C18O J=2-1 lines on sub-parsec scales across the cloud. We directly measure the ratio of CO integrated intensity to dust extinction to derive the CO X-factor at over 1e5 independent locations in the cloud. Confirming an earlier study, we find that no single 12CO X-factor can characterize the molecular gas in the cold ( Tdust<20K) regions of the cloud that account for most of its mass. We are able to derive a single-valued X-factor for all three CO isotopologues in the warm ( Tdust>25 K ) material that is spatially coincident with an HII region surrounding the star LKHa101. We derive LTE CO column densities for 13CO and C18O since we find both lines are relatively optically thin. In the warm cloud material CO is completely in the gas phase and we are able to recover the total 13CO and C18O abundances. Using CO abundances and deep Herschel observations, we measure lower bounds to the freeze-out of CO onto dust across the whole cloud finding some regions having CO depleted by a factor of >20. We construct the first maps of depletion that span the extent of a giant molecular cloud. Using these maps we identify 75 depletion-defined cores and discuss their physical nature.
