化学在中国II。--AB Aur盘的分子含量低
Chemistry in Disks. II. -- Poor molecular content of the AB Aur disk
摘要：
我们研究的分子内容和化学的拱盘周围的赫比格Ae星AB Aur在（亚）毫米波长。我们的目标是重建AB Aur盘的化学历史和组成，并将其与低质量，较冷的金牛T星周围的盘进行比较。我们观察AB Aur磁盘与IRAM平台德布尔干涉仪在C-和D-配置中的CS，HCN，C2 H，CH 3OH，HCO+，和CO同位素的旋转线。使用迭代最小化技术，观测柱密度和丰度的推导。这些值进一步比较与一个先进的化学模型的结果，该模型是基于一个稳态的喇叭形盘结构的垂直温度梯度，和气体颗粒化学网络与表面反应。我们在1- 0跃迁中坚定地检测到HCO+，暂时检测到HCN，而没有检测到CS，C2 H和CH 3OH。所观察到的HCO+和13 CO柱密度以及HCN，CS，C2 H，和CH 3OH的柱密度的上限与建模结果和以前的研究是很好的协议。AB Aur盘具有更多的CO，但与DM Tau盘相比，其他分子种类的丰度较低。这主要是由中央赫比格A0恒星的强烈紫外线照射引起的，这导致了一个更热的磁盘，其中CO冻结不会发生，因此表面形成复杂的含CO分子可能会受到抑制。
英文摘要：
We study the molecular content and chemistry of a circumstellar disk surrounding the Herbig Ae star AB Aur at (sub-)millimeter wavelengths. Our aim is to reconstruct the chemical history and composition of the AB Aur disk and to compare it with disks around low-mass, cooler T Tauri stars. We observe the AB Aur disk with the IRAM Plateau de Bure Interferometer in the C- and D- configurations in rotational lines of CS, HCN, C2H, CH3OH, HCO+, and CO isotopes. Using an iterative minimization technique, observed columns densities and abundances are derived. These values are further compared with results of an advanced chemical model that is based on a steady-state flared disk structure with a vertical temperature gradient, and gas-grain chemical network with surface reactions. We firmly detect HCO+ in the 1--0 transition, tentatively detect HCN, and do not detect CS, C2H, and CH3OH. The observed HCO+ and 13CO column densities as well as the upper limits to the column densities of HCN, CS, C2H, and CH3OH are in good agreement with modeling results and those from previous studies. The AB Aur disk possesses more CO, but is less abundant in other molecular species compared to the DM Tau disk. This is primarily caused by intense UV irradiation from the central Herbig A0 star, which results in a hotter disk where CO freeze out does not occur and thus surface formation of complex CO-bearing molecules might be inhibited.
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