A Survey of Dense Cores in the Orion A Cloud
A Survey of Dense Cores in the Orion A Cloud
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DOI：
10.1086/519484
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发表时间：
2009-02
期刊：
影响因子：
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通讯作者：
N. Ikeda;K. Sunada;Y. Kitamura
中科院分区：
文献类型：
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作者：
N. Ikeda;K. Sunada;Y. Kitamura
我们利用Nobeyama 45 m射电望远镜和25个波束阵列接收系统（BEARS），在1.5° × 0.5°的大面积范围内对猎户座A分子云进行了H13 CO+（J = 1-0）的岩心观测。这次调查的独特之处在于，大面积（~48 pc 2）的云被21“（0.05 pc）的高空间分辨率和深度积分（1 σ ~ 0.1 K，T）覆盖，导致1.6 M的核心质量检测。H_（13）CO ~+（J = 1-0）发射的形态与850 μm连续谱发射的形态非常相似。我们用clumpfind算法从我们的数据中识别出236个密集核心。核心接近维里平衡，无论他们是热或湍流。我们预测的初始质量函数（IMF）的核心质量函数，考虑到二进制的形成和混乱沿着视线，并发现，这个IMF同意与猎户座星云星团IMF的星星形成效率为~ 40%。因此，我们认为IMF是在致密核形成时确定的。此外，我们还发现了三个速度宽度较大的核心，明显比其他核心的速度宽度更宽，仅朝向M42 H II区域，这表明来自H II区域的能量输入增加了速度宽度。由于这三个核心可以产生最大质量的恒星，由于它们的大质量吸积率，猎户座A云下一代的大质量星星形成很可能是由附近的恒星活动引起的。
We have carried out an H13CO+(J = 1-0) core survey in a large area of 1.5° × 0.5°, covering the whole region of the Orion A molecular cloud, using the Nobeyama 45 m radio telescope with the 25 Beam Array Receiver System (BEARS). This survey is unique in that a large area (~48 pc2) of the cloud was covered with a high spatial resolution of 21'' (0.05 pc) and with a deep integration (1 σ ~ 0.1 K in T), resulting in a core mass detection of 1.6 M☉. The morphology of the H13CO+(J = 1-0) emission is very similar to that of the 850 μm continuum emission. We identified 236 dense cores from our data with the clumpfind algorithm. The cores are close to virial equilibrium, independent of whether they are thermal or turbulent. We predict an initial mass function (IMF) from the core mass function, considering binary formation and confusion along the line of sight, and find that this IMF agrees well with the Orion Nebula cluster IMF for a star formation efficiency of ~40%. Therefore, we suggest that the IMF is determined at the time of the dense core formation. Furthermore, we discovered three cores with large velocity widths, significantly wider than those of the other cores, only toward the M42 H II region, suggesting that the energy input from the H II region increases the velocity width. Since the three cores can produce the most massive stars, owing to their large mass accretion rates, massive star formation in the next generation in the Orion A cloud is likely to be caused by nearby stellar activity.