论文标题
第一个ch $ _ {3} $ d检测0/i i proto-brown矮人：ch $ _ {4} $丰度的约束
First CH$_{3}$D detection in Class 0/I proto-brown dwarfs: constraints on CH$_{4}$ abundances
论文作者
论文摘要
我们报告了$ {\ it J} _ {\ it k} $ = 1 $ _ {0} $ - 0 $ _ {0} $ CH $ _ {3} $ d的旋转过渡线向三个/I Proto-Brown brown dwarfs（proto-bds）从iram 30 m观察到三个/i Proto-brown dwarfs（proto-bds）。假设旋转温度为25 K，则ch $ _ {3} $ d丰度（相对于H $ _ {2} $）在（2.3---14.5）$ 10 $^{ - 7} $的范围内。 ch $ _ {4} $丰度从Ch $ _ {3} $ D丰度得出，并假设DCO $^+$/hco $^+$比率在（0.05---4.8）$ 10 $^$^{ - 5} $的范围内。 CH $ _ {3} $ D的气相形成通过CH $ _2 $ _2 $ D $^+$以10 $^{8} $ -10 $^{10} $ cm $^{ - 3} $增强，我们的观察结果可能是在原始的和热的地区探测了原始的和温暖的区域。热和/或非热解吸可以返回ch $ _ {3} $ d和ch $ _ {4} $分子在早期阶段形成的谷物表面上形成的分子到气相。气相的丰度表明在原始BD中，碳链化学反应是温暖的碳链化学，其中碳链分子在不冷热（$ \ sim $ 20-30 K）区域中合成，靠近中心来源。
We report the first detection in the ${\it J}_{\it K}$ = 1$_{0}$ - 0$_{0}$ rotational transition line of CH$_{3}$D towards three Class 0/I proto-brown dwarfs (proto-BDs) from IRAM 30 m observations. Assuming a rotational temperature of 25 K, the CH$_{3}$D abundances (relative to H$_{2}$) are in the range of (2.3--14.5) $\times$ 10$^{-7}$. The CH$_{4}$ abundances derived from the CH$_{3}$D abundances and assuming the DCO$^+$/HCO$^+$ ratios are in the range of (0.05--4.8) $\times $10$^{-5}$. The gas-phase formation of CH$_{3}$D via CH$_2$D$^+$ is enhanced at high densities of 10$^{8}$--10$^{10}$ cm$^{-3}$ and our observations are likely probing the innermost dense and warm regions in proto-BDs. Thermal and/or non-thermal desorption can return the CH$_{3}$D and CH$_{4}$ molecules formed at an early stage on grain surfaces to the gas-phase. The gas phase abundances are indicative of warm carbon-chain chemistry in proto-BDs where carbon-chain molecules are synthesized in a lukewarm ($\sim$20-30 K) region close to the central source.
