论文标题
0/i原始棕色矮人中的氘化学和D/H比
Deuterium chemistry and D/H ratios in Class 0/I proto-brown dwarfs
论文作者
论文摘要
我们已经对16级0/I Proto-Brown矮人（Proto-BDS）和4个扁平/II类Brown Dwarfs进行了首次对几种氘化物种进行了首次广泛的观测调查。在DCO $^{+} $（3-2），DCN（3-2），DNC（3-2）和N $ _ {2} $ D} $ D $^{+} $（3-2）中，使用IRAM 300M望远镜获得观测值。 dco $^{+} $/h $^{13} $ co $^{+} $，dcn/h $^{13} $ cn和dnc/hn $^{13} $ c比率比较较高，并且比dco $^{+} $/hco $/hco $^{+/hn and and and and and and and and and，and and and and， 分别。从这些分子得出的原始BD的平均D/H比在$ \ sim $ 0.02-3的范围内。需要低温气相离子 - 分子螺旋龙转移和晶粒表面反应，以解释增强的氘分馏。非常致密和冷（$ n_ {h_ {2}} $ $ \ geq $ 10 $^{6} $ cm $^{ - 3} $，t $ \ leq $ 10 k $ 10 K）内部为这些内核提供有效的蠕虫分离的适当条件。 D/H比与CO耗竭因子之间没有相关性，除了DCN/HCN的比率外，由于DCN和HCN分子的峰发射区域的差异可能显示出很强的抗相关性。在跨度范围跨度$ \ sim $ 0.002--40 l $ _ {\ odot} $的范围内，我们发现了较高的dco $^{+} $/hco $^{+} $^{+} $（r = -0.7）和dcn/hcn/hcn/hcn/hcn/hcn（r = -0.6）的趋势（r = -0.6）比例（r = -0.6）比例（r = -0.6）ratc（r = -0.6） dnc/hn $^{13} $ c（r = -0.1）比率，较低的n $ _ {2} $ d $^{+} $/n $ _ {2} $ _ {2} $ h $^{+} $比率（r = 0.6）在原始BDS中与Protostars相比。只有一个II类Brown Dwarf显示了DCO $^{+} $（3-2）行中的排放。 D/H比与进化阶段之间看不到相关性。
We have conducted the first extensive observational survey of several deuterated species in 16 Class 0/I proto-brown dwarfs (proto-BDs) and 4 Class Flat/Class II brown dwarfs. Observations were obtained with the IRAM 30m telescope in the DCO$^{+}$ (3-2), DCN (3-2), DNC (3-2), and N$_{2}$D$^{+}$ (3-2) lines. The DCO$^{+}$/H$^{13}$CO$^{+}$, DCN/H$^{13}$CN, and DNC/HN$^{13}$C ratios are comparatively higher and show a narrower range than the DCO$^{+}$/HCO$^{+}$, DCN/HCN, and DNC/HNC ratios, respectively. The mean D/H ratios for the proto-BDs derived from these molecules are in the range of $\sim$0.02-3. Both low-temperature gas-phase ion-molecule deuteron transfer and grain surface reactions are required to explain the enhanced deuterium fractionation. The very dense and cold ($n_{H_{2}}$ $\geq$10$^{6}$ cm$^{-3}$, T $\leq$10 K) interior of the proto-BDs provide the suitable conditions for efficient deuterium fractionation in these cores. There is no correlation between the D/H ratios and the CO depletion factor, with the exception of the DCN/HCN ratios that show a strong anti-correlation possibly due to the difference in the peak emitting regions of the DCN and HCN molecules. Over a wide range in the bolometric luminosities spanning $\sim$0.002--40 L$_{\odot}$, we find a trend of higher DCO$^{+}$/HCO$^{+}$ (r = -0.7) and DCN/HCN (r = -0.6) ratios, nearly constant DNC/HNC (r = -0.4) and DNC/HN$^{13}$C (r = -0.1) ratios, lower N$_{2}$D$^{+}$/N$_{2}$H$^{+}$ ratios (r = 0.6) in the proto-BDs compared to protostars. Only one Class II brown dwarf shows emission in the DCO$^{+}$ (3-2) line. No correlation is seen between the D/H ratios and the evolutionary stage.
