论文标题
确认L1451毫米流出：SIO系列和CH $ _3 $ OH MASER检测
Confirmation of the outflow in L1451-mm: SiO line and CH$_3$OH maser detections
论文作者
论文摘要
现在已经在星际培养基中搜索了近二十年来在理论上预测的第一级静水压核（FHSC）的观测对应物。将它们与其他类型的更具进化但仍然嵌入的物体区分开来仍然是一个挑战，因为这些物体的寿命很短，很小，并且嵌入了密集的茧中。找到它们的可能导致它们是这些对象启动的流出的表征。我们观察到具有NOEMA干涉仪的L1451-MM FHSC候选者，以研究几个分子的发射。对CH $ _3 $ OH检测线进行了非本地热力学平衡分析，以检索中央源周围发射区域的物理条件，以及CH $ _3 $ _3 $ OH，SIO，CS和H $ _2 $ CO CO列列密度。在目标分子中，我们检测到C-C $ _3 $ h $ _2 $，ch $ _3 $ oh，cs，c $^{34} $ s，so，so，dcn，dco $^+$，H $ _2 $ CO，HC $ _3 $ N，HDCO和SIO。其中一条甲醇线似乎是一条Maser线。 L1451-mm中该类I级的检测和SIO系列支持低速和紧凑的流出。甲醇热线的激发条件也与冲击兼容（H $ _2 $密度为$ \ sim 3 \ times 10^6 $ 〜cm $^{ - 3} $，温度高于40〜K）。尽管这些低速流出是通过某些FHSC模型预测的，但这些模型也预测电击温度将低于20 〜k，即不蒸发甲醇。此外，预测的速度不会侵蚀晶粒并在气相中释放硅。因此，我们得出的结论是，这些新的观察结果有利于以下假设：L1451-mm将处于非常早期的原始阶段，几乎在天空平面上以比观察到的更高的速度发射流出。
The observational counterparts of theoretically predicted first hydrostatic cores (FHSC) have been searched for in the interstellar medium for nearly two decades now. Distinguishing them from other types of more evolved but still embedded objects remains a challenge because these objects have a short lifetime, are small, and embedded in a dense cocoon. One possible lead to finding them is the characterization of the outflows that are launched by these objects. We observed the L1451-mm FHSC candidate with the NOEMA interferometer in order to study the emission of several molecules. A nonlocal thermodynamic equilibrium analysis of the CH$_3$OH detected lines was performed to retrieve the physical conditions of the emitting region around the central source, together with the CH$_3$OH, SiO, CS, and H$_2$CO column densities. Of the targeted molecules, we detected lines of c-C$_3$H$_2$, CH$_3$OH, CS, C$^{34}$S, SO, DCN, DCO$^+$, H$_2$CO, HC$_3$N, HDCO, and SiO. One of the methanol lines appears to be a maser line. The detection of this class I maser and the SiO line in L1451-mm support the presence of a low-velocity and compact outflow. The excitation conditions of the thermal lines of methanol are also compatible with shocks (H$_2$ density of $\sim 3\times 10^6$~cm$^{-3}$ and a temperature higher than 40~K). Although these low-velocity outflows are theoretically predicted by some models of FHSC, these models also predict the shock temperature to be below 20~K, that is, not evaporating methanol. In addition, the predicted velocities would not erode the grains and release silicon in the gas phase. We therefore conclude that these new observations favor the hypothesis that L1451-mm would be at a very early protostellar stage, launching an outflow nearly on the plane of the sky with a higher velocity than is observed.
