The latest developments in astrochemistry have shown how some molecular species can be used as tools to study the early stages of the solar-type star formation process. Among them, particularly relevant are interstellar complex organic molecules (iCOMs) and deuterated molecules. Their analysis gives us information on the present and past history of the protostellar objects. Among the protostellar evolutionary stages, Class I protostars represent a perfect laboratory where the initial conditions for the planet formation process can be studied. Indeed, from a physical point of view, the Class I stage is the bridge between the Class 0 phase, dominated by the accretion process, and the protoplanetary disk phase, when planets form. Despite their importance, few observations of Class I protostars exist, and very little is known about their chemical content. In this paper we review the (few) existing observations of iCOMs and deuterated species in Class I protostars. In addition, we present new observations of deuterated cyanoacetylene and thioformaldehyde toward the Class I protostar SVS13-A. These new observations allow us to better understand the physical and chemical structure of SVS13-A and compare the cyanoacetylene and thioformaldehyde deuteration with other sources in different evolutionary phases.

中文翻译：

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天体化学作为跟踪原恒星演化的工具：第一阶段

天体化学的最新进展表明如何将某些分子物种用作研究太阳型恒星形成过程早期阶段的工具。其中，特别相关的是星际复杂有机分子（iCOM）和氘代分子。他们的分析为我们提供了有关原恒星物体的当前和过去历史的信息。在原星演化阶段中，I级原星代表了一个完美的实验室，可以在这里研究行星形成过程的初始条件。实际上，从物理角度来看，I级阶段是由增生过程主导的0级阶段与行星形成时的原行星盘阶段之间的桥梁。尽管很重要，但几乎没有关于I级星标的观察，对其化学含量知之甚少。在本文中，我们回顾了ICOM类恒星中iCOMs和氘代物种的现有（很少）观察结果。此外，我们对I类原恒星SVS13-A给出了氘化氰基乙炔和硫代甲醛的新观察结果。这些新发现使我们能够更好地了解SVS13-A的物理和化学结构，并将氰基乙炔和硫代甲醛氘与其他来源处于不同进化阶段的产品进行比较。