A C18O STUDY OF THE ORIGIN OF THE POWER-LAW NATURE IN THE INITIAL MASS FUNCTION
A C18O STUDY OF THE ORIGIN OF THE POWER-LAW NATURE IN THE INITIAL MASS FUNCTION
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DOI：
10.1088/0004-637x/705/1/l95
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发表时间：
2009-10
期刊：
影响因子：
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通讯作者：
N. Ikeda;Y. Kitamura
中科院分区：
文献类型：
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作者：
N. Ikeda;Y. Kitamura
我们对猎户座A云OMC-1区的20′ × 20′区域进行了C ~（18）O（J = 1-0）成图观测。我们确定了65个C18 O核，它们的平均半径、速度宽度（半高宽）和LTE质量分别为0.18 ± 0.03 pc、0.40 ± 0.15 km s−1和7.2 ± 4.5 M。考虑到C18 O丰度的不确定性，所有的核都最有可能受到重力束缚。我们推导出了C18 O的核心质量函数，它显示了幂律的行为高于5 M的反冲。最佳拟合的幂律指数为−2.3 ± 0.3，这与OMC-1区域的致密核心质量函数和恒星初始质量函数（IMF）一致。这一一致性强烈地表明，IMF的幂律形式已经在密度为1003 cm−3时确定，由C18 O（J = 1-0）线追踪。因此，我们建议应该在密度小于103 cm−3的稀薄云结构中寻找IMF的起源。
We have performed C18O (J = 1–0) mapping observations of a 20′ × 20′ area of the OMC-1 region in the Orion A cloud. We identified 65 C18O cores, which have a mean radius, a velocity width in FWHM, and an LTE mass of 0.18 ± 0.03 pc, 0.40 ± 0.15 km s−1, and 7.2 ± 4.5 M☉, respectively. All the cores are most likely to be gravitationally bound by considering the uncertainty in the C18O abundance. We derived a C18O core mass function, which shows a power-law-like behavior above 5 M☉. The best-fit power-law index of −2.3 ± 0.3 is consistent with those of the dense core mass functions and the stellar initial mass function (IMF) previously derived in the OMC-1 region. This agreement strongly suggests that the power-law form of the IMF has been already determined at the density of ∼103 cm−3, traced by the C18O (J = 1–0) line. Consequently, we propose that the origin of the IMF should be searched in tenuous cloud structures with densities of less than 103 cm−3.