论文标题
Cloudlet捕获模型的非对称分子发射线在TMC-1A中使用ALMA观察到的模型
Cloudlet Capture Model for Asymmetric Molecular Emission Lines Observed in TMC-1A with ALMA
论文作者
论文摘要
TMC-1A是带有年轻原恒星IRA，IRAS 04365+2353的原始源，在分子发射线中显示了几分100 AU量表的高度不对称特征。在CS（$ j = 5 $ -4）线上，蓝移发射要比红移一行要强得多。鉴于Cloudlet接近我们，可以解释不对称的气体积聚并采用Cloudlet捕获的形式。原恒星的重力将Cloudlet转化为流，并沿流动变化。在围龙之前，应在periastron之前对Cloudlet的发射进行蓝光，而应在Periastron之后进行红移。如果Cloudlet的主要部分尚未到达Periastron，那么前者应该占主导地位。我们执行流体动力学模拟以检查场景的有效性。如果Cloudlet的轨道倾斜到磁盘平面，我们的数值模拟可以再现观察到的不对称性。倾斜度可以解释在C $^{18} $ O（$ j $ = 2-1）线排放中观察到的缓慢的输入速度。由于实际云可能具有不均匀的密度分布，因此这种发作的积聚可能发生在各种原始核心中。我们还讨论了Cloudlet捕获对相关对象的观察的含义。
TMC-1A is a protostellar source harboring a young protostar, IRAS 04365+2353, and shows a highly asymmetric features of a few 100 au scale in the molecular emission lines. Blue-shifted emission is much stronger in the CS ($J=5$-4) line than red-shifted one. The asymmetry can be explained if the gas accretion is episodic and takes the form of cloudlet capture, given the cloudlet approached toward us. The gravity of the protostar transforms the cloudlet into a stream and changes its velocity along the flow. The emission from the cloudlet should be blue-shifted before the periastron, while it should be red-shifted after the periastron. If a major part of cloudlet has not reached the periastron, the former should be dominant. We perform hydrodynamical simulations to examine the validity of the scenario. Our numerical simulations can reproduce the observed asymmetry if the orbit of the cloudlet is inclined to the disk plane. The inclination can explain the slow infall velocity observed in the C$^{18}$O ($J$=2-1) line emission. Such episodic accretion may occur in various protostellar cores since actual clouds could have inhomogeneous density distribution. We also discuss the implication of the cloudlet capture on observations of related objects.
