TMC-1中HCCCN的双取代同位素异构体：D13CCCN、DC13CCN、DCC13CN、DCCC15N、H13C13CCN、H13CC13CN、HC13C13CN、HCC13C15N和HC13CC15N的探测
Doubly substituted isotopologues of HCCCN in TMC-1: Detection of D13CCCN, DC13CCN, DCC13CN, DCCC15N, H13C13CCN, H13CC13CN, HC13C13CN, HCC13C15N, and HC13CC15N
AI总结：
本研究利用Yebes 40米望远镜的QUIJOTE巡天，首次在TMC-1中探测到9种HCCCN双取代同位素异构体，结合多波段观测建模分析了其丰度、分馏效应及空间分布，发现氘代物种示踪了分子云更冷的区域。
摘要：
我们利用Yebes 40米望远镜开展的QUIJOTE谱线巡天观测，首次在星际空间中朝向TMC-1的氰基聚炔峰探测到了9种HCCCN双取代同位素异构体的完整样本。我们通过7毫米窗口内的J=4-3和J=5-4跃迁谱线，探测到了D13CCCN、DC13CCN、DCC13CN、DCCC15N、H13C13CCN、H13CC13CN、HC13C13CN、HCC13C15N和HC13CC15N。此外，我们分别利用Yebes 40米望远镜在7毫米波段、IRAM 30米望远镜在3毫米波段探测到的谱线，通过大速度梯度模型，对HCCCN及其单取代同位素异构体的发射进行了广泛分析。在H2数密度为1e4 cm-3、动力学温度为10 K的条件下，两个波段中推导得到的所有同位素异构体的柱密度结果一致。我们观测到HCC13CN以及其他含有与氮原子相邻的13C原子的双同位素异构体存在13C分馏，而DCCCN的三种13C取代物种的C/13C丰度比相近。这表明HCCCN的氘代同位素异构体存在额外的化学分异效应。最后，我们展示了利用Yebes 40米望远镜观测到的单取代物种的J=4-3和J=5-4谱线的空间分布。DCCCN空间分布的发射峰相较于HCCCN以及13C、15N同位素异构体的发射峰偏移了40角秒。除了氘代物种存在不同的形成路径外，我们还推测这种由氘分馏导致的差异在低温下更高效，因此氘代物种示踪了分子云中更冷的区域。
英文摘要：
We report the first detection in space of a complete sample of nine doubly substituted isotopologues of HCCCN towards the cyanopolyyne peak of TMC-1 using observations of the QUIJOTE line survey taken with the Yebes 40 m telescope. We detected D13CCCN, DC13CCN, DCC13CN, DCCC15N, H13C13CCN, H13CC13CN, HC13C13CN, HCC13C15N, and HC13CC15N through their J=4-3 and J=5-4 lines in the 7 mm window. In addition, we present an extensive analysis of the emission of HCCCN and its singly substituted isotopologues through a large velocity gradient model of the lines detected at 7 mm and 3 mm using the Yebes 40 m and the IRAM 30 m telescopes, respectively. The derived column densities for all the isotopologues are consistent in the two spectral bands for an H2 volume density of 1e4 cm-3 and a kinetic temperature of 10 K. Whereas we observed a 13C fractionation for HCC13CN and other double isotopologues with a 13C atom adjacent to the nitrogen atom, we derived similar C/13C abundance ratios for the three 13C substituted species of DCCCN. This suggests additional chemical discrimination for deuterated isotopologues of HCCCN. Finally, we present the spatial distribution of the J=4-3 and J=5-4 lines from the singly substituted species observed with the Yebes 40 m telescope. The emission peak of the spatial distribution of DCCCN appears to be displaced by 40'' with respect to that of HCCCN and the 13C and 15N isotopologues. In addition to a different formation route for the deuterated species, we could also expect that this differentiation owing to the deuterium fractionation is more efficient at low temperatures, and therefore, that deuterated species trace a colder region of the cloud.
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