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arXiv 1608.08446astro-ph.GA
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具有复杂空间和运动学结构的块状岩芯的多频研究

Multi-frequency Studies of Massive Cores with Complex Spatial and Kinematic Structures

L. E. Pirogov, V. M. Shul'ga, I. I. Zinchenko, P. M. Zemlyanukha, O. N. Patoka, M. Thomasson

摘要:

在频率范围为$\sim 85-89$ GHz的各种分子谱线中,已经观察到五个大质量恒星形成区域。所研究的区域拥有致密的核心,其中包含年轻的恒星物体。核的物理参数进行了估计,包括动力学温度($\sim 20-40$ K),发射区的大小($\sim 0.1-0.6$ pc),和维里质量($\sim 40-500 M_{\odot}$)。在局部热力学平衡近似下计算了各种分子的柱密度和丰度。在99.982+4.17的核心,与最弱的IRAS源相关,其特征是分子丰度降低。分子谱线宽度随着离核心中心距离的增加而减小($b$)。对于$b\ga 0.1$ ~pc,依赖性$ΔV(b)$接近幂律($\propto b^{-p}$),其中$p$根据对象从$\sim 0.2$变化到$\sim 0.5$。在四个核心中,光学厚的HCN(1- 0)和HCO $^+$(1- 0)线的不对称性表明了沿着视线的系统运动:两个核心中的坍缩和另外两个核心中的膨胀。对坍缩核心吸积率的近似估计表明,形成中的恒星质量超过太阳质量。

英文摘要:

Five regions of massive star formation have been observed in various molecular lines in the frequency range $\sim 85-89$ GHz. The studied regions possess dense cores, which host young stellar objects. The physical parameters of the cores are estimated, including kinetic temperatures ($\sim 20-40$ K), sizes of the emitting regions ($\sim 0.1-0.6$ pc), and virial masses ($\sim 40-500 M_{\odot}$). Column densities and abundances of various molecules are calculated in the local thermodynamical equilibrium approximation. The core in 99.982+4.17, associated with the weakest IRAS source, is characterized by reduced molecular abundances. Molecular line widths decrease with increasing distance from the core centers ($b$). For $b\ga 0.1$~pc, the dependences $ΔV(b)$ are close to power laws ($\propto b^{-p}$), where $p$ varies from $\sim 0.2$ to $\sim 0.5$, depending on the object. In four cores, the asymmetries of the optically thick HCN(1--0) and HCO$^+$(1--0) lines indicate systematic motions along the line of sight: collapse in two cores and expansion in two others. Approximate estimates of the accretion rates in the collapsing cores indicate that the forming stars have masses exceeding the solar mass.

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