标题： 冷核L694的动力学演化上的化学约束 显示英文标题

标题： Chemical constraints on the dynamical evolution of the cold core L694

摘要： 在恒星形成区域，分子云的历史和动力学决定了化学组成的趋势。 特别是冰的形成受到物理条件演化的的影响，这可能导致同一云中不同的冰组成。 在密度大于1e4 cm-3、温度低于15 K且紫外辐射低于G0的冷核心中，大多数复杂有机分子（COMs）在尘埃颗粒表面形成，并通过非热机制释放回气相。 研究气相和固相可以帮助观测者对冷核心的化学和动力学演化施加约束。 我们呈现了对使用IRAM 30米望远镜观测的冷核心L694的研究。 观测到的物种包括CO（及其同位素）和CH3OH。 我们应用了一个反向非LTE辐射转移代码，以通过从目标分子跃迁的光谱参数以及从档案观测中得到的物理参数推导出检测到物种的柱密度，从而获得气相丰度。 这使我们能够探测分子丰度随密度和视觉消光的变化。 同时，我们运行了化学模型（静态和动态）以通过直接比较观测结果与模型输出来限制核心的演化时间。 然后我们将冷核心L429-C和L694的组成进行了比较。 L694中的气相丰度都表现出一个共同的耗竭轮廓（耗竭因子有较大变化），因为该核心被识别为比L429-C处于更先进的（内流）状态。 然而，这两个核心的物理参数非常相似，导致我们在静态模型中得到接近的演化时间尺度。 动态模型无法在高密度下重现CO的气相丰度，预测的演化时间尺度比静态模型短得多。 显示英文摘要

摘要： In star-forming regions, molecular cloud history and dynamics set the trend in the chemical composition. Ice formation, in particular, is affected by the evolution of physical conditions, which can lead to different ice compositions within the same cloud. In cold cores with medium densities >1e4 cm-3, low temperatures <15 K, and low UV radiation <G0, most COMs are formed on dust grain surfaces and are released back into the gas phase through non-thermal mechanisms. Studying both gas- and solid-phases can help observers to add constraints on the chemical and dynamical evolution of cold cores. We present a study of the cold core L694, observed with the IRAM 30m telescope. Observed species include CO (and its isotopologues) and CH3OH. We applied an inverted non-LTE radiative transfer code in order to obtain gas-phase abundances by deriving the column densities of the detected species from the spectroscopic parameters of the targeted molecular transitions, and from physical parameters derived from archival observations. This allowed us to probe the molecular abundances as a function of density and visual extinction. In parallel, we ran chemical models (both static and dynamic) to constrain the evolution time of the core by directly comparing the observations with the model outputs. We then compared the compositions of the cold cores L429-C and L694. The gas-phase abundances in L694 all exhibit a common depletion profile (with high variability in the depletion factor), as the core is identified to be in a more advanced (infalling) state compared to L429-C. The physical parameters of the two cores are, however, very similar, leading to close evolutionary timescales in our static models. The dynamical model fails to reproduce the CO gas-phase abundances at high density, predicting an evolutionary timescale that is too short compared to static models.