arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0905.1747astro-ph.GA
收藏

极低质量0类原恒星系统HH 211亚角秒分辨率下的自转和外流运动

Rotation and Outflow motions in the very low-mass Class 0 protostellar system HH 211 at subarcsecond resolution

Chin-Fei Lee, Naomi Hirano, Aina Palau, Paul T. P. Ho, Tyler L. Bourke, Qizhou Zhang, Hsien Shang

摘要:

HH 211是附近一个年轻的原恒星系统,有高度准直的喷流。我们用亚毫米阵列(SMA)在352 GHz连续谱、SiO(J=8-7)和HCO+(J=4-3)发射中以高达~ 0.2”的分辨率绘制了它。连续谱源现在被分解为两个源,SMM 1和SMM 2,间隔约为84 AU。SMM 1位于喷流的中心,可能是追踪驱动喷流的原恒星周围的(内部)尘埃盘。SMM 2位于SMM 1的西南方,可能是一个围绕着一个小的双星伴星的圆盘。在SMM 1周围的HCO+中可以看到一个扁平的圆盘,半径约为80 AU,垂直于喷流轴。它的速度结构与自转运动一致,可以用开普勒定律拟合,得到原恒星的质量约为50+-15木星质量(棕矮星的质量)。因此,这颗原恒星可能是已知拥有准直喷流和旋转扁平圆盘的最低质量源。在HCOP+中,在从盘状盘延伸的喷流轴周围观察到小尺度(~ 200 AU)低速(~ 2 km/s)流出。它似乎与圆盘的旋转方向相同,并可能带走圆盘的部分角动量。在距离SMM 1约100 AU的SiO中可以看到喷流。它被认为是一个“C形”弯曲。它的横向宽度小于~ 40 AU,速度为~ 170+-60 km/s。在它最里面的一对结上,可以看到一个可能的速度梯度,在~ 10 AU处约为0.5 km/s,与圆盘的旋转方向一致。如果这个梯度是喷流的真实旋转梯度的上限,那么喷流带走的角动量非常小,约为5 AU km/s,因此必须从靠近共转半径的圆盘的最内边缘发射。

英文摘要:

HH 211 is a nearby young protostellar system with a highly collimated jet. We have mapped it in 352 GHz continuum, SiO (J=8-7), and HCO+ (J=4-3) emission at up to ~ 0.2" resolution with the Submillimeter Array (SMA). The continuum source is now resolved into two sources, SMM1 and SMM2, with a separation of ~ 84 AU. SMM1 is seen at the center of the jet, probably tracing a (inner) dusty disk around the protostar driving the jet. SMM2 is seen to the southwest of SMM1 and may trace an envelope-disk around a small binary companion. A flattened envelope-disk is seen in HCO+ around SMM1 with a radius of ~ 80 AU perpendicular to the jet axis. Its velocity structure is consistent with a rotation motion and can be fitted with a Keplerian law that yields a mass of ~ 50+-15 Jupiter mass (a mass of a brown dwarf) for the protostar. Thus, the protostar could be the lowest mass source known to have a collimated jet and a rotating flattened envelope-disk. A small-scale (~ 200 AU) low-speed (~ 2 km/s) outflow is seen in HCOP+ around the jet axis extending from the envelope-disk. It seems to rotate in the same direction as the envelope-disk and may carry away part of the angular momentum from the envelope-disk. The jet is seen in SiO close to ~ 100 AU from SMM1. It is seen with a "C-shaped" bending. It has a transverse width of <~ 40 AU and a velocity of ~ 170+-60 km/s. A possible velocity gradient is seen consistently across its innermost pair of knots, with ~ 0.5 km/s at ~ 10 AU, consistent with the sense of rotation of the envelope-disk. If this gradient is an upper limit of the true rotational gradient of the jet, then the jet carries away a very small amount of angular momentum of ~ 5 AU km/s and thus must be launched from the very inner edge of the disk near the corotation radius.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑