化学活性L1157流出物的团簇结构
The clumpy structure of the chemically active L1157 outflow
摘要:
我们提出了高空间分辨率的地图,获得与高原德布尔干涉仪,蓝色的L1157流出瓣。我们在3 mm处观察到四条谱线,即CH_3OH(2_K-1_K),HC_3 N(11- 1 - 0),HCN(1-0)和OCS(7-6)。此外,在CS(2-1),CH_3OH(2_1-1_1)A-和~(34)SO(3_2-2_1)中也观察到了较好的空间分辨率。这些高空间分辨率的观测结果表明,在所有的示踪剂非常丰富的结构,揭示了一个cluberous结构的气体叠加到一个扩展的排放。事实上,以前的IRAM-30 m单碟观测发现的三个团块已被分解为几个子团块,并在流出物中发现了新的团块。这些团块与旋进射流驱动的两个激波所产生的两个空腔有关。特别是,最接近原恒星的团块位于年轻腔的壁上,具有清晰的拱形形状,而最远的团块具有略微不同的观测特征,表明它们与较老的冲击事件有关。观测到的各组分的发射峰分布在叶瓣的不同部位,东团较亮的是HC_3 N(11- 1 - 0)、HCN(1-0)和CS(2-1),西团较亮的是CH_3OH(2_K-1_K)、OCS(7-6)和~(34)SO(3_2-2_1)。线发射中的这种峰值位移表明,在小尺度下,沿外流波瓣的物理条件和/或化学成分的变化,可能与激波活动和外流的进动有关。特别是,我们观察到去耦的一氧化硅和甲醇排放,常见的冲击示踪剂,在B1块位于顶点的弓冲击产生的第二次冲击插曲。
英文摘要:
We present high spatial resolution maps, obtained with the Plateau de Bure Interferometer, of the blue lobe of the L1157 outflow. We observed four lines at 3 mm, namely CH3OH (2_K-1_K), HC3N (11-10), HCN (1-0) and OCS (7-6). Moreover, the bright B1 clump has also been observed at better spatial resolution in CS (2-1), CH3OH (2_1-1_1)A-, and 34SO (3_2-2_1). These high spatial resolution observations show a very rich structure in all the tracers, revealing a clumpy structure of the gas superimposed to an extended emission. In fact, the three clumps detected by previous IRAM-30m single dish observations have been resolved into several sub-clumps and new clumps have been detected in the outflow. The clumps are associated with the two cavities created by two shock episodes driven by the precessing jet. In particular, the clumps nearest the protostar are located at the walls of the younger cavity with a clear arch-shape form while the farthest clumps have slightly different observational characteristics indicating that they are associated to the older shock episode. The emission of the observed species peaks in different part of the lobe: the east clumps are brighter in HC3N (11-10), HCN (1-0) and CS (2-1) while the west clumps are brighter in CH3OH(2_K-1_K), OCS (7-6) and 34SO (3_2-2_1). This peak displacement in the line emission suggests a variation of the physical conditions and/or the chemical composition along the lobe of the outflow at small scale, likely related to the shock activity and the precession of the outflow. In particular, we observe the decoupling of the silicon monoxide and methanol emission, common shock tracers, in the B1 clump located at the apex of the bow shock produced by the second shock episode.
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