The molecular gas content of the Pipe Nebula I. Direct evidence of outflow-generated turbulence in B59?
The molecular gas content of the Pipe Nebula I. Direct evidence of outflow-generated turbulence in B59?
复制标题
管状星云 I 的分子气体含量。B59 中流出产生湍流的直接证据？
DOI：
10.1051/0004-6361/201219240
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发表时间：
2012
影响因子：
6.5
通讯作者：
Duarte-Cabral A
中科院分区：
文献类型：
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作者：
Duarte-Cabral A
背景星星形成区域可能具有许多共同的特征，但重力、磁场、大尺度动力学和原恒星反馈之间的特定相互作用将对每个区域的星星形成历史产生影响。外流反馈的重要性是一个特别有争议的话题，因为我们还没有了解它们对云和星星形成的影响的细节。目的烟斗星云是一个附近的分子云，拥有B59区域作为其唯一活跃的恒星形成团块。本文主要研究B59的整体动力学、温度结构和外流气体，目的是揭示原恒星外流的局部和整体影响.方法利用James Clerk Maxwell望远镜上的HARP，在12 CO J = 3 → 2跃迁的B59区域，研究外流的运动学和能量学，和相同的过渡of 13 CO和C18 O研究的整体动态的环境云，气体的物理性质，和层次结构的region.ResultsThe B59区域有一个总的~ 30 M的冷和静止的材料，主要是重力约束，整个窄线宽。在B59内部的非恒星形成区域中，如此低的湍流水平表明了云的内在初始条件。另一方面，在原恒星附近，观测到外流的影响，C18 O谱线宽度从~0.3 km s-1增加到~1 km s-1，13 CO激发温度增加~2-3 K。外流的影响在低柱密度物质中也很明显，这些物质显示出当外流弓形激波穿透云层时被它们塑造的迹象。这种结构是很容易明显的云的树状图分析，并表明，当使用这种技术分解云的结果进行仔细的解释是need.ConclusionsThe低质量的B59连同其固有的静态气体和少量的原恒星，允许识别的特定区域的流出物从嵌入式源相互作用的致密气体。我们的研究表明，外流是一个重要的机制，注入和维持超音速湍流在亚秒差距尺度。我们发现，不到一半的流出能量作为气体的湍流能量沉积，然而，这种湍流能量足以减缓该区域的崩溃。
ContextStar forming regions may share many characteristics, but the specific interplay between gravity, magnetic fields, large-scale dynamics, and protostellar feedback will have an impact on the star formation history of each region. The importance of feedback from outflows is a particular subject to debate, as we are yet to understand the details of their impact on clouds and star formation.AimsThe Pipe Nebula is a nearby molecular cloud hosting the B59 region as its only active star-forming clump. This paper focuses on the global dynamics of B59, its temperature structure, and its outflowing gas, with the goal of revealing the local and global impact of the protostellar outflows.MethodsUsing HARP at theJames Clerk MaxwellTelescope, we have mapped the B59 region in theJ= 3 → 2 transition of12CO to study the kinematics and energetics of the outflows, and the same transitions of13CO and C18O to study the overall dynamics of the ambient cloud, the physical properties of the gas, and the hierarchical structure of the region.ResultsThe B59 region has a total of ~30M⊙of cold and quiescent material, mostly gravitationally bound, with narrow line widths throughout. Such low levels of turbulence in the non-star-forming regions within B59 are indicative of the intrinsic initial conditions of the cloud. On the other hand, close to the protostars the impact of the outflows is observed as a localised increase of both C18O line widths from ~0.3 km s-1to ~1 km s-1, and13CO excitation temperatures by ~2–3 K. The impact of the outflows is also evident in the low column density material which shows signs of being shaped by the outflow bow shocks as they pierce their way out of the cloud. Much of this structure is readily apparent in a dendrogram analysis of the cloud and demonstrates that when decomposing clouds using such techniques a careful interpretation of the results is needed.ConclusionsThe low mass of B59 together with its intrinsically quiescent gas and small number of protostars, allows the identification of specific regions where the outflows from the embedded sources interact the dense gas. Our study suggests that outflows are an important mechanism for injecting and sustaining supersonic turbulence at sub-parsec size scales. We find that less than half of the outflow energy is deposited as turbulent energy of the gas, however this turbulent energy is sufficient to slow down the collapse of the region.