arXiv 0709.38432007-09-24astro-ph

MWC 1080附近年轻星团中的致密分子气体--大质量恒星的规则

Dense Molecular Gas In A Young Cluster Around MWC 1080 -- Rule Of The Massive Star

Shiya Wang, Leslie W. Looney, Wolfgang Brandner, Laird M. Close

备注：: 42 pages, 5 tables, and 13 figures, accepted for publication in ApJ
DOI：: 10.1086/523846

摘要：

我们提出CS $J = 2 \to 1$，$^{13}$ CO $J = 1 \to 0$，和C $^{18}$ O $J = 1 \to 0$，观测与10元素伯克利伊利诺伊马里兰协会（BIMA）阵列对年轻的集群周围的Be星MWC 1080。这些观察结果显示，$\sim$半长轴和半短轴尺寸为0.3和0.05 pc，$\sim$ 45 $\arcdeg$位置角为双锥形流出腔。这些转变追踪致密气体，这可能是流出空腔的扫气，而不是剩余的原生气体或流出气体。这种气体是凝块的，一共有32个凝块。已识别的团块近似受重力约束，并与标准等温球体密度一致，这表明它们可能是坍缩的原恒星核心。气体运动学表明，存在速度梯度，这意味着腔和MWC 1080的倾斜的影响。稠密气体的运动学也受到来自MWC 1080的外流或恒星风的影响，低质量的团块可能比高质量的团块受到MWC 1080的影响更大。此外，与孤立的低质量恒星形成核心相比，低质量的星团成员倾向于形成在密度更大、更动荡的核心中。这是由于附近正在形成的大质量恒星的贡献，如外流或恒星风。因此，我们得出结论，在像MWC 1080系统的集群中，来自大质量恒星的影响在出生云的运动学和动力学以及低质量集群成员的形成中主导了恒星形成环境。这项研究提供了对MWC 1080对其出生云的影响的见解，并表明与孤立的恒星形成相比，星团中的低质量恒星形成环境不同。

英文摘要：

We present CS $J = 2 \to 1$, $^{13}$CO $J = 1 \to 0$, and C$^{18}$O $J = 1 \to 0$, observations with the 10-element Berkeley Illinois Maryland Association (BIMA) Array toward the young cluster around the Be star MWC 1080. These observations reveal a biconical outflow cavity with size $\sim$ 0.3 and 0.05 pc for the semimajor and semiminor axis and $\sim$ 45$\arcdeg$ position angle. These transitions trace the dense gas, which is likely the swept-up gas of the outflow cavity, rather than the remaining natal gas or the outflow gas. The gas is clumpy; thirty-two clumps are identified. The identified clumps are approximately gravitationally bound and consistent with a standard isothermal sphere density, which suggests that they are likely collapsing protostellar cores. The gas kinematics suggests that there exists velocity gradients implying effects from the inclination of the cavity and MWC 1080. The kinematics of dense gas has also been affected by either outflows or stellar winds from MWC 1080, and lower-mass clumps are possibly under stronger effects from MWC 1080 than higher-mass clumps. In addition, low-mass cluster members tend to be formed in the denser and more turbulent cores, compared to isolated low-mass star-forming cores. This results from contributions of nearby forming massive stars, such as outflows or stellar winds. Therefore, we conclude that in clusters like the MWC 1080 system, effects from massive stars dominate the star-forming environment in both the kinematics and dynamics of the natal cloud and the formation of low-mass cluster members. This study provides insights into the effects of MWC 1080 on its natal cloud, and suggests a different low-mass star forming environment in clusters compared to isolated star formation.

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