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arXiv 2009.00407astro-ph.GAastro-ph.SR
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星前核中氘代分子的合成观测

Synthetic observations of deuterated molecules in massive prestellar cores

Joaquin Zamponi F., Andrea Giannetti, Stefano Bovino, Giovanni Sabatini, Dominik R. G. Schleicher, Bastian Körtgen, Stefan Reissl, Sebastian Wolf

备注：
12 pages, 8 figures, submitted to MNRAS
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摘要：

年轻的大质量恒星通常被发现嵌入在密集的大质量分子团中，并且以高度模糊和遥远而闻名。在它们的形成过程中，氘化被认为是非常早期形成阶段的潜在良好指标。在这项工作中，我们测试的邻H $_2$ D $^+$ $J_{\rm {K_a, K_c}} = 1_{10}$ - $1_{11} $基态跃迁的可观测性进行干涉和单碟合成观测使用磁流体动力学模拟的高质量坍缩分子核心，包括氘化学。我们研究了不同的进化时间和源距离（从1到7千秒差距），以估计信息损失时，从合成观测推断的列密度的模型中的列密度进行比较。我们模仿单碟观测考虑一个APEX类光束和干涉观测使用CASA和假设最紧凑的配置的ALMA天线。我们发现，对于中心集中的密度分布，在高分辨率ALMA观测（$\leqslant$ 1”）的情况下，柱密度被低估了约51%，而在APEX观测（17”）的情况下，柱密度被低估了高达90%。干涉仪获取的值更接近真实值，然而，由于缺乏短基线，其有限的空间采样导致大尺度结构的贡献损失。我们的结论是，o-H $_2$ D $^+$的发射在遥远的大质量致密的核心是微弱的，将需要从$\sim$ 1至$\sim$ 7小时的观测距离为1和7千秒差距，分别达到14 $σ$检测在最好的情况下。此外，从这样的观测中得到的柱密度肯定会受到单碟光束稀释和干涉仪空间滤波的影响。

英文摘要：

Young massive stars are usually found embedded in dense massive molecular clumps and are known for being highly obscured and distant. During their formation process, deuteration is regarded as a potentially good indicator of the very early formation stages. In this work, we test the observability of the ground-state transition of ortho-H$_2$D$^+$ $J_{\rm {K_a, K_c}} = 1_{10}$-$1_{11} $ by performing interferometric and single-dish synthetic observations using magneto-hydrodynamic simulations of high-mass collapsing molecular cores, including deuteration chemistry. We studied different evolutionary times and source distances (from 1 to 7 kpc) to estimate the information loss when comparing the column densities inferred from the synthetic observations to the column densities in the model. We mimicked single-dish observations considering an APEX-like beam and interferometric observations using CASA and assuming the most compact configuration for the ALMA antennas. We found that, for centrally concentrated density distributions, the column densities are underestimated by about 51% in the case of high-resolution ALMA observations ($\leqslant$1") and up to 90% for APEX observations (17"). Interferometers retrieve values closer to the real ones, however, their finite spatial sampling results in the loss of contribution from large-scale structures due to the lack of short baselines. We conclude that, the emission of o-H$_2$D$^+$ in distant massive dense cores is faint and would require from $\sim$1 to $\sim$7 hours of observation at distances of 1 and 7 kpc, respectively, to achieve a 14$σ$ detection in the best case scenario. Additionally, the column densities derived from such observations will certainly be affected by beam dilution in the case of single-dishes and spatial filtering in the case of interferometers.

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