Discovery of a Giant Molecular Loop in the Central Region of NGC 253
Discovery of a Giant Molecular Loop in the Central Region of NGC 253
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DOI：
10.3847/1538-4357/ac58f7
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发表时间：
2021-06
期刊：
影响因子：
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通讯作者：
R. Konishi;R. Enokiya;Y. Fukui;K. Muraoka;K. Tokuda;T. Onishi
中科院分区：
文献类型：
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作者：
R. Konishi;R. Enokiya;Y. Fukui;K. Muraoka;K. Tokuda;T. Onishi
NGC 253是一个SAB（s）c型的星暴星系，由于其在无与伦比的近距离上的高活动性而越来越受到人们的关注。它的能量事件表现为中心分子区的垂直气体特征，恒星反馈被认为是驱动引擎。为了进一步研究这一活动的细节，我们对阿尔马存档的12 CO（J = 3 − 2）排放数据进行了运动学分析，其分辨率最高为103 pc。我们发现，在中心分子区的非旋转的气体成分之一，显示出一个环状结构的半径为200 pc。环状结构与一个星星星团有关，而星团不在环状结构内，不太可能是环状结构形成的驱动力。进一步，我们发现NGC 253的棒势似乎太弱，不能通过偏心轨道驱动气体运动。作为替代方案，我们框架的情况下，磁加速的帕克不稳定性是负责创建的环状结构。我们发现，所观察到的环状结构的性质是类似于那些在银河系中，并认为，最近的磁流体力学模拟提供支持的图片具有100 μG的磁场强度。我们认为，集群的形成是由下降的气体的循环，这是符合一个典型的动力学时间尺度的循环100万年的足点。
NGC 253 is a starburst galaxy of SAB(s)c type with increasing interest because of its high activity at unrivaled closeness. Its energetic event is manifested as the vertical gas features in its central molecular zone, for which stellar feedback was proposed as the driving engine. In order to pursue details of the activity, we have undertaken a kinematic analysis of the ALMA archive data of 12CO(J = 3 − 2) emission at the highest resolution ∼3 pc. We revealed that one of the non-rotating gas components in the central molecular zone shows a loop-like structure of ∼200 pc radius. The loop-like structure is associated with a star cluster, whereas the cluster is not inside the loop-like structure and is not likely as the driver of the loop-like structure formation. Further, we find that the bar potential of NGC 253 seems to be too weak to drive the gas motion by the eccentric orbit. As an alternative, we frame a scenario that magnetic acceleration by the Parker instability is responsible for the creation of the loop-like structure. We show that the observed loop-like structure properties are similar to those in the Milky Way, and argue that recent magneto-hydrodynamics simulations lend support for the picture having the magnetic field strength of ≳100 μG. We suggest that cluster formation was triggered by the falling gas to the footpoint of the loop, which is consistent with a typical dynamical timescale of the loop ∼1 Myr.