There is mounting evidence that the composition and structure of planetary systems are intimately linked to their birth environments. During the past decade, several spectral surveys probed the chemistry of the earliest stages of star formation and of late planet-forming disks. However, very little is known about the chemistry of intermediate protostellar stages, i.e. Class I Young Stellar Objects (YSOs), where planet formation may have already begun. We present here the first results of a 3mm spectral survey performed with the IRAM-30m telescope to investigate the chemistry of a sample of seven Class I YSOs located in the Taurus star-forming region. These sources were selected to embrace the wide diversity identified for low-mass protostellar envelope and disk systems. We present detections and upper limits of thirteen small ($N_{\rm atoms}\leq3$) C, N, O, and S carriers - namely CO, HCO$^+$, HCN, HNC, CN, N$_2$H$^+$, C$_2$H, CS, SO, HCS$^+$, C$_2$S, SO$_2$, OCS - and some of their D, $^{13}$C, $^{15}$N, $^{18}$O, $^{17}$O, and $^{34}$S isotopologues. Together, these species provide constraints on gas-phase C/N/O ratios, D- and $^{15}$N-fractionation, source temperature and UV exposure, as well as the overall S-chemistry. We find substantial evidence of chemical differentiation among our source sample, some of which can be traced back to Class I physical parameters, such as the disk-to-envelope mass ratio (proxy for Class I evolutionary stage), the source luminosity, and the UV-field strength. Overall, these first results allow us to start investigating the astrochemistry of Class I objects, however, interferometric observations are needed to differentiate envelope versus disk chemistry.

中文翻译：

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对 I 类 YSO 中小有机物的 3 毫米化学探索

越来越多的证据表明行星系统的组成和结构与其诞生环境密切相关。在过去的十年中，一些光谱调查探索了恒星形成和晚期行星形成盘的最早阶段的化学成分。然而，人们对中间原恒星阶段的化学知之甚少，即 I 类年轻恒星天体 (YSO)，其中行星的形成可能已经开始。我们在此展示了使用 IRAM-30m 望远镜进行的 3mm 光谱调查的第一个结果，以研究位于金牛座恒星形成区域的七个 I 类 YSO 样本的化学成分。选择这些来源是为了包含为低质量原恒星包膜和盘系统确定的广泛多样性。我们提出了十三个小 ($N_{\rm atom}\leq3$) C、N、O 和 S 载体的检测和上限 - 即 CO、HCO$^+$、HCN、HNC、CN、N$_2$ H$^+$, C$_2$H, CS, SO, HCS$^+$, C$_2$S, SO$_2$, OCS - 以及他们的一些 D, $^{13}$C, $ ^{15}$N、$^{18}$O、$^{17}$O 和 $^{34}$S 同位素体。这些物质共同限制了气相 C/N/O 比率、D-和 $^{15}$N-分馏、源温度和紫外线照射以及整体 S-化学。我们在源样本中发现了大量化学差异的证据，其中一些可以追溯到 I 类物理参数，例如磁盘与包络的质量比（I 类进化阶段的代表）、源光度和紫外线场强。总的来说，这些初步结果使我们能够开始研究 I 类天体的天体化学，然而，