Structured velocity field in the inner envelope of B335: ALMA observations of rare CO isotopologues
Structured velocity field in the inner envelope of B335: ALMA observations of rare CO isotopologues
复制标题
B335 内层的结构化速度场：稀有 CO 同位素异体物的 ALMA 观测
DOI：
10.1051/0004-6361/202140754
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发表时间：
2021
影响因子：
6.5
通讯作者：
M. Padovani
中科院分区：
文献类型：
--
作者：
V. Cabedo;A. Maury;J. Girart;M. Padovani
研究0类天体非常重要，因为它可以描述星星形成过程开始时的动力学过程，并确定导致坍缩结果的物理机制。对致密气体示踪剂的观测可以描述直接参与恒星形成过程的气体的关键运动学特征，例如流入、流出或旋转。本工作旨在研究0类原恒星天体B335的分子线速度分布，并试图对该天体的星周气体中发生的下落运动施加约束。给出了C ^{17} O（1-0），C ^{18} O（1-0）和C ^{12}CO（2-1）跃迁的观测结果，并分析了包络半径在100 ~ 860 Au范围内的光谱轮廓。C$^{17}$O排放呈双峰型，分布在复杂的速度场中.这两个峰值与探测区域内震源的系统速度相差0.2至1 km/s ^{-1}$。C$^{17}$O发射的光学深度已被估计，并发现小于1，这表明两个速度峰跟踪两个不同的速度分量的气体在内部信封。在排除可能产生复杂速度模式的运动（如旋转和流出）后，得出结论，即流入正在产生速度场。由于由内而外的对称崩溃不能解释这些观察到的配置文件，它建议，这些是由非各向同性吸积从信封到中央源沿着流出空腔壁。
Studying Class 0 objects is very important, as it allows to characterize dynamical processes at the onset of the star formation process, and to determine the physical mechanisms responsible for the outcome of the collapse. Observations of dense gas tracers allow the characterization of key kinematics of the gas directly involved in the star-formation process, such as infall, outflow or rotation. This work aims at investigating the molecular line velocity profiles of the Class 0 protostellar object B335 and attempts to put constraints on the infall motions happening in the circumstellar gas of the object.} Observations of C$^{17}$O (1-0), C$^{18}$O (1-0) and $^{12}CO$ (2-1) transitions are presented and the spectral profiles are analyzed at envelope radii between 100 and 860 au. C$^{17}$O emission presents a double peaked line profile distributed in a complex velocity field. Both peaks present an offset of 0.2 to 1 km s$^{-1}$ from the systemic velocity of the source in the probed area. The optical depth of the C$^{17}$O emission has been estimated and found to be less than 1, suggesting that the two velocity peaks trace two distinct velocity components of the gas in the inner envelope. After discarding possible motions that could produce the complex velocity pattern, such as rotation and outflow, it is concluded that infall is producing the velocity field. Because inside-out symmetric collapse cannot explain those observed profiles, it is suggested that those are produced by non-isotropic accretion from the envelope into the central source along the outflow cavity walls.