Methyl carbamate CH$_3$OC(O)NH$_2$ is an isomer of glycine. Quantum chemical analyses show that methyl carbamate is more stable isomer than glycine. Because of this, there could be a higher chance for methyl carbamte to exist in the interstellar medium as compared to glycine. Despite immense searches, till now glycine has not been detected in the ISM, therefore it is worthwhile to search its isomer methyl carbamate. In this paper, we present the constraints of methyl carbamate formation under the interstellar conditions. Large complex organic molecules are favorably produced in hot-corino environments of low mass protostars. We for the first time carried out astrochemical modeling focusing on the formation of methyl carbamate in physical conditions similar to hot-corino objects. Consequently, we examined ALMA archival data for existing spectral line observations toward hot corinos NGC1333 IRAS 4A2 and IRAS 16293B. Within the common spectral range towards these sources, we found three features are possibly related to the spectral transitions of methyl carbamate and consequently estimate the upper limit of column densities. Results of chemical modeling are consistent with the observational upper limit of estimated column density/abundance toward the sources. This may hint the validation of the proposed formation mechanism. Future observations using telescope like ngVLA may confirm the presence of MC toward the hot corinos.

中文翻译：

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热 Corinos 中氨基甲酸甲酯（一种甘氨酸异构体）的形成和丰度的限制

氨基甲酸甲酯 CH$_3$OC(O)NH$_2$ 是甘氨酸的异构体。量子化学分析表明，氨基甲酸甲酯是比甘氨酸更稳定的异构体。因此，与甘氨酸相比，星际介质中氨基甲酸甲酯存在的可能性更高。尽管进行了大量搜索，但到目前为止，还没有在 ISM 中检测到甘氨酸，因此值得对其异构体甲基氨基甲酸酯进行搜索。在本文中，我们介绍了星际条件下氨基甲酸甲酯形成的限制条件。大的复杂有机分子在低质量原恒星的热科里诺环境中有利地产生。我们首次进行了天体化学建模，重点是在类似于热柯里诺天体的物理条件下形成氨基甲酸甲酯。最后，我们检查了 ALMA 档案数据，以获取对热 corinos NGC1333 IRAS 4A2 和 IRAS 16293B 的现有谱线观测。在这些光源的常见光谱范围内，我们发现三个特征可能与氨基甲酸甲酯的光谱跃迁有关，因此估计了柱密度的上限。化学建模的结果与估计柱密度/丰度的观测上限一致。这可能暗示了所提出的形成机制的验证。未来使用像 ngVLA 这样的望远镜进行的观察可能会证实 MC 存在于热的科里诺斯。我们发现三个特征可能与氨基甲酸甲酯的光谱跃迁有关，因此估计了柱密度的上限。化学建模的结果与估计柱密度/丰度的观测上限一致。这可能暗示了所提出的形成机制的验证。未来使用像 ngVLA 这样的望远镜进行的观察可能会证实 MC 存在于热的科里诺斯。我们发现三个特征可能与氨基甲酸甲酯的光谱跃迁有关，因此估计了柱密度的上限。化学建模的结果与估计柱密度/丰度的观测上限一致。这可能暗示了所提出的形成机制的验证。未来使用像 ngVLA 这样的望远镜进行的观察可能会证实 MC 存在于热的科里诺斯。