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名稱Title
2020天文年會
中研院天文所 國際會議廳

論文摘要

ALMA Observations toward the S-shaped Outflow and the Envelope around NGC1333 IRAS4A2

[ Poster ]

Chen-Yu Chuang (NTU/ASIAA); Yusuke Aso (KASI); Naomi Hirano (ASIAA); Shingo Hirano (Kyushu University); Masahiro N. Machida(Kyushu University)

NGC1333 IRAS4A is a well-studied Class 0 protobinary system embedded in a circumbinary envelope. Each protostar of the binary, IRAS4A1 and IRAS4A2, ejects its outflow toward the north and the south. To investigate the system in more detail, we analyzed ALMA archival data of SO (6_5-5_4), SO (7_6-6_5), and CO (2-1) lines. In the last ASROC meeting, we reported the S-shaped outflow driven by IRAS4A2, which consists of a flattened envelope surrounding the central source and two outflow lobes connected to both edges of it. The flattened envelope has an opposite velocity gradient to that of the circumbinary envelope. The S-shaped morphology is obvious in the high velocity range, whereas it is less significant in the low velocity range showing two conical cavities. The observed features are reproduced by the magnetohydrodynamic simulation of the collapsing core whose magnetic field direction is misaligned to the rotational axis. Our simulation shows that the intensity of the outflow lobes is enhanced on one side, resulting in the formation of S-shaped morphology. Here we present the simulation result including the effects of SO abundance and sublimation temperature. The new model can reproduce the S-shape morphology more obvious than the previous one with constant SO abundance. In addition, the new model better reproduce the morphological difference between low and high velocity components, i.e. the S-shaped enhancement is weaker at a low velocity whereas the enhancement is stronger at a high velocity. The opposite velocity gradients in the flattened envelope and the circumbinary envelope can be explained as the rotation and inflowing motion, respectively. Addtionally, we also discovered a previously unknown extremely high velocity component at ±45—70 km/s near IRAS4A2 with CO.