论恒星形成区中氮化磷的起源
On the origin of phosphorus nitride in star-forming regions
摘要：
我们提出了多个过渡的观察PN对一个样本的9个大规模致密的核心在不同的演化阶段。利用不同激发条件下的跃迁，我们首次发现PN的激发温度在5-30 K之间。为了研究PN形成的主要化学途径（表面化学与气相化学）和主要的解吸机制（热与冲击），我们将我们的结果与从分子跟踪不同的化学和物理条件（SiO，SO，CH 3OH和N2 H+）得到的结果进行了比较。在9个靶中，有6个靶的PN线轮廓与SiO和SO的PN线轮廓有很好的相关性，这表明PN可能是由激波引起的尘埃粒子溅射释放出来的。PN丰度与SiO和SO丰度之间存在微弱但统计上显著的正趋势，证实了这一发现。然而，在三个物体中，PN线没有高速机翼的迹象，这表明PN的另一种起源。总的来说，我们的研究结果表明，PN的起源是不是唯一的，因为它可以形成在原恒星冲击，但也在更冷，更安静的气体通过替代途径。
英文摘要：
We present multi-transition observations of PN towards a sample of nine massive dense cores in different evolutionary stages. Using transitions with different excitation conditions, we have found for the first time that the excitation temperatures of PN are in the range 5-30 K. To investigate the main chemical route for the PN formation (surface-chemistry vs. gas-phase chemistry), and the dominant desorption mechanism (thermal vs. shock), we have compared our results with those obtained from molecules tracing different chemical and physical conditions (SiO, SO, CH3OH, and N2H+). We have found that the PN line profiles are very well correlated with those of SiO and SO in six out of the nine targets, which indicates that PN may be released by sputtering of dust grains due to shocks. This finding is corroborated by a faint but statistically significant positive trend between the PN abundance and those of SiO and SO. However, in three objects the PN lines have no hints of high velocity wings, which indicates an alternative origin of PN. Overall, our results indicate that the origin of PN is not unique, as it can be formed in protostellar shocks, but also in colder and more quiescent gas through alternative pathways.
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