First detection of ND in the solar-mass protostar IRAS16293-2422
First detection of ND in the solar-mass protostar IRAS16293-2422
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首次在太阳质量原恒星 IRAS16293-2422 中检测到 ND
DOI：
10.1051/0004-6361/201015102
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发表时间：
2010
影响因子：
6.5
通讯作者：
Bacmann A
中科院分区：
文献类型：
--
作者：
Bacmann A
在过去的十年中，在描述导致在ISM中观察到的氘分馏增强的过程方面取得了很大的进展，特别是在恒星形成区域的冷、致密部分，如原恒星包层。饱和分子和离子的D/H比非常高。然而，对于氘在自由基中的分馏所知甚少，尽管简单的自由基通常代表了更复杂的饱和分子形成的中间阶段。亚胺根nhh就是气相合成氨的一种中间物质。然而，许多这些光分子在亚毫米波段有它们的基本跃迁，它们的探测受到这些波长的大气不透明度的阻碍。Herschel/HIFI为研究从地面无法观察到的物种的氘化和形成机制提供了独特的机会。目的寻找亚胺根的氘化自由基ND，以确定亚胺根的氘分馏，约束亚胺根的氘化机理。方法利用herschelkey计划CHESS （ChemicalHErschelSurvey of Star forming regions）的1a （480-560 GHz）、3b （858-961 GHz）和4a （949-1061 GHz）波段的外差仪器HIFI对太阳质量为0级的原恒星IRAS16293-2422进行观测。结果在新生的原恒星发射的连续谱背景下，在522.1和546.2 GHz的吸收波段，通过亚胺基自由基ND的2个超精细跃迁基团（N= 0-1），检测到ND的氘化形式。其氢化对应物NH的3组超细组分也在吸收中被检测到。吸收来自冷包层，在冷包层中有许多氘化物质已被证明是丰富的。NH柱密度估计为~2 × 1014cm-2， ND柱密度估计为~ 1.3 × 1014cm-2。我们得到了一个非常高的氘分馏，[ND]/[NH]的比率在30到100%之间。结论亚胺根的氘分馏与其他分子的氘分馏具有相同的数量级，表明亚胺根的氘分馏机制是有效的。我们讨论了ND的两种可能的形成途径，即N+与HD的反应或与NH的氘核/质子交换。
ContextIn the past decade, much progress has been made in characterising the processes leading to the enhanced deuterium fractionation observed in the ISM and in particular in the cold, dense parts of star forming regions such as protostellar envelopes. Very high molecular D/H ratios have been found for saturated molecules and ions. However, little is known about the deuterium fractionation in radicals, even though simple radicals often represent an intermediate stage in the formation of more complex, saturated molecules. The imidogen radical NH is such an intermediate species for the ammonia synthesis in the gas phase. Many of these light molecules however have their fundamental transitions in the submillimetre domain and their detection is hampered by the opacity of the atmosphere at these wavelengths.Herschel/HIFI represents a unique opportunity to study the deuteration and formation mechanisms of species not observable from the ground.AimsWe searched here for the deuterated radical ND in order to determine the deuterium fractionation of imidogen and constrain the deuteration mechanism of this species.MethodsWe observed the solar-mass Class 0 protostar IRAS16293-2422 with the heterodyne instrument HIFI in Bands 1a (480–560 GHz), 3b (858–961 GHz), and 4a (949–1061 GHz) as part of theHerschelkey programme CHESS (ChemicalHErschelSurvey of Star forming regions).ResultsThe deuterated form of the imidogen radical ND was detected and securely identified with 2 hyperfine component groups of its fundamental transition (N= 0–1) at 522.1 and 546.2 GHz, in absorption against the continuum background emitted from the nascent protostar. The 3 groups of hyperfine components of its hydrogenated counterpart NH were also detected in absorption. The absorption arises from the cold envelope, where many deuterated species have been shown to be abundant. The estimated column densities are ~2 × 1014cm-2for NH and ~ 1.3 × 1014cm-2for ND. We derive a very high deuterium fractionation with an [ND]/[NH] ratio of between 30 and 100%.ConclusionsThe deuterium fractionation of imidogen is of the same order of magnitude as that in other molecules, which suggests that an efficient deuterium fractionation mechanism is at play. We discuss two possible formation pathways for ND, by means of either the reaction of N+with HD, or deuteron/proton exchange with NH.
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DOI：
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发表时间：
1993
期刊：
影响因子：
--
作者：
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DOI：
--
发表时间：
2003
期刊：
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DOI：
--
发表时间：
2001
期刊：
影响因子：
--
作者：
S. Rodgers;S. Charnley
通讯作者：
S. Charnley
DOI：
--
发表时间：
2002
期刊：
The Astrophysical Journal
影响因子：
--
作者：
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DOI：
10.1086/175915
发表时间：
1995-07
期刊：
The Astrophysical Journal
影响因子：
--
作者：
Ewine;-F.;Van Dishoeck;L. Geoffrey;-A.;Blake;David J. Jansen;T. Groesbeck
通讯作者：
Ewine;-F.;Van Dishoeck;L. Geoffrey;-A.;Blake;David J. Jansen;T. Groesbeck