论文标题
GUAPOS项目：G31.41+0.31无偏的ALMA光谱观测调查-I。C $ _ {2} $ h $ _ {4} $ o $ o $ $ $ _ {2} $
The GUAPOS project: G31.41+0.31 Unbiased ALMA sPectral Observational Survey -- I. Isomers of C$_{2}$H$_{4}$O$_{2}$
论文作者
论文摘要
了解星际培养基中生命的基础的前体可以在星形区域达到的化学复杂性程度，这是天文学的目标之一。因此，需要具有较大带宽和高光谱分辨率的无偏光谱调查，以解决化学丰富来源中的线条混合并鉴定复杂的有机分子。这种观察已成功进行，主要是向银河中心进行的，该区域显示出特殊的环境条件。我们对位于银河系中心外部最丰富的最丰富的热分子核之一的3mm进行了无偏光谱调查，位于高质量恒星形成区G31.41+0.31中。在第一篇论文中，我们介绍调查并讨论C $ _ {2} $ H $ _ {4} $ o $ $ _ {2} $的3个异构体的检测：甲基甲酸盐，甘油醛和乙酸。观测与ALMA进行，并覆盖整个频段3，从84到116 GHz，其角度分辨率为$ 1.2^{''} $ x $ x $ 1.2^{'''} $，频谱分辨率为$ \ sim0.488 $ MHz。已经用软件XCLASS分析了3个分子的过渡。检测到所有三个异构体，与文献中的来源相比，G31中G31中的甲基甲酸盐和乙酸丰度是最高的。在三个异构体的乙酸中，发射的大小变化，表现出最紧密的发射，而甲基构成最延伸的甲基发射。与化学模型的比较表明，必须需要在G31中形成甲基甲酸盐的晶曲面途径，而对于糖醛，这两种情况都是可行的。提出的乙酸的晶粒表面反应无法重现这项工作中观察到的丰度，而由于较大的不确定性，应进一步测试气相的情况。
Understanding the degree of chemical complexity that can be reached in star-forming regions, together with the identification of precursors of the building blocks of life in the interstellar medium, is one of the goals of astrochemistry. Unbiased spectral surveys with large bandwidth and high spectral resolution are thus needed, to resolve line blending in chemically rich sources and identify complex organic molecules. This kind of observations has been successfully carried out, mainly towards the Galactic Center, a region that shows peculiar environmental conditions. We present an unbiased spectral survey at 3mm of one of the most chemically rich hot molecular cores located outside the Galactic Center, in the high-mass star-forming region G31.41+0.31. In this first paper, we present the survey and discuss the detection of the 3 isomers of C$_{2}$H$_{4}$O$_{2}$: methyl formate, glycolaldehyde and acetic acid. Observations were carried out with ALMA and cover the entire Band 3 from 84 to 116 GHz with an angular resolution of $1.2^{''}$x$1.2^{''}$ and a spectral resolution of $\sim0.488$ MHz. The transitions of the 3 molecules have been analyzed with the software XCLASS. All three isomers were detected and methyl formate and acetic acid abundances in G31 are the highest detected up to now, if compared to sources in literature. The size of the emission varies among the three isomers with acetic acid showing the most compact emission while methyl formate the most extended. The comparison with chemical models suggests the necessity of grain-surface routes for the formation of methyl formate in G31, while for glycolaldehyde both scenarios could be feasible. Proposed grain-surface reaction for acetic acid is not able to reproduce the observed abundance in this work, while gas-phase scenario should be further tested due to large uncertainties.
