论文标题
30多拉德斯中的共销分子气体质量
The CO-dark molecular gas mass in 30 Doradus
论文作者
论文摘要
确定气体在星系中转化为恒星的效率需要准确确定分子气体质量的总储层。然而，尽管是宇宙中最丰富的分子，但H $ _2 $通过直接观察的检测很具有挑战性，必须使用间接方法来估计总分子气体储量。这些通常是基于示踪剂（例如CO或DUST）的缩放关系，通常以银河系进行校准。然而，证据表明这些扩展关系在环境上依赖性依赖。特别是，预计在金属罚款和/或强烈的UV IRRADIADIAD环境中，常用的Co-to-H $ _2 $转换因子（x $ _ {\ rm co} $）预计将更高。我们使用来自离子和中性气体和中性气体以及Meudon光解离区模型的远红外良好结构线的新的Sofia/Fifi-LS观察，以限制30个大麦芽云中30多拉多斯的巨大星形形成区域中气体的物理性能和结构R136。我们将该值与从地面CO观测值和基于灰尘的估计值推断的分子气体质量进行比较，以量化这种极端环境对分子气体常用示踪剂的影响。我们发现，强辐射场与周围气体的半极金属性相结合，是造成大量“涂层”分子气体的储层，在采用标准x $ _ {\ rm co} $中，在这个庞大的X $ _ {\ rm co} $中，总h $ _2 $ _2 $ _2 $ _2 $ _2 $（> 75％）的一小部分。
Determining the efficiency with which gas is converted into stars in galaxies requires an accurate determination of the total reservoir of molecular gas mass. However, despite being the most abundant molecule in the Universe, H$_2$ is challenging to detect through direct observations and indirect methods have to be used to estimate the total molecular gas reservoir. These are often based on scaling relations from tracers such as CO or dust, and are generally calibrated in the Milky Way. Yet, evidence that these scaling relations are environmentally dependent is growing. In particular, the commonly used CO-to-H$_2$ conversion factor (X$_{\rm CO}$) is expected to be higher in metal-poor and/or strongly UV-irradiated environments. We use new SOFIA/FIFI-LS observations of far-infrared fine structure lines from the ionised and neutral gas and the Meudon photodissociation region model to constrain the physical properties and the structure of the gas in the massive star-forming region of 30 Doradus in the Large Magellanic Cloud, and determine the spatially resolved distribution of the total reservoir of molecular gas in the proximity of the young massive cluster R136. We compare this value with the molecular gas mass inferred from ground-based CO observations and dust-based estimates to quantify the impact of this extreme environment on commonly used tracers of the molecular gas. We find that the strong radiation field combined with the half-solar metallicity of the surrounding gas are responsible for a large reservoir of "CO-dark" molecular gas, leaving a large fraction of the total H$_2$ gas (> 75%) undetected when adopting a standard X$_{\rm CO}$ factor in this massive star-forming region.
