A Complete Search for Dense Cloud Cores in Taurus
A Complete Search for Dense Cloud Cores in Taurus
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DOI：
10.1086/341347
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发表时间：
2002-08
期刊：
影响因子：
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通讯作者：
T. Onishi;A. Mizuno;A. Kawamura;K. Tachihara;Y. Fukui
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文献类型：
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作者：
T. Onishi;A. Mizuno;A. Kawamura;K. Tachihara;Y. Fukui
我们提出了一个H13 CO + J = 1-0调查致密的分子凝聚金牛座的结果。观测是在名古屋大学4米望远镜进行的广泛的C18 O调查的基础上，用45米望远镜在野边山进行的。目前的调查是纯粹基于分子线的观察，从而提供了最广泛和统一的高密度凝聚的样本。我们探测到55个H13 CO+凝聚，其中44个是无星的。这些无星凝聚体是致密的（R = 0.1 pc）和高密度的（R = 105 cm-3），因此在星星形成之前极有可能是原恒星凝聚体的候选者。这些无星致密凝聚体的显著特征是质谱的陡峭斜率（dN/dM ~ M-2.5，对于3.5 M返< M < 20.1 M返）。在均匀的星星形成效率的假设下，光谱类似于恒星的初始质量函数（IMF）的质量为几个太阳质量。这表明，恒星IMF是相对较低密度的核心碎裂过程的结果。对无星凝聚的统计分析得出凝聚的寿命约为4 × 105年，比自由落体的时间尺度长几倍。与磁通量损失时间相比，这种短的时间尺度可以指示时间尺度由湍流的耗散时间尺度确定。
We present the results of an H13CO+ J = 1-0 survey for dense molecular condensations in Taurus. The observations were carried out with the 45 m telescope at Nobeyama on the basis of an extensive C18O survey made with the 4 m telescope at Nagoya University. The present survey is based purely on molecular line observations and thus provides the most extensive and uniform sample of high-density condensations. We detected 55 H13CO+ condensations, of which 44 are starless. These starless condensations are compact (R ≲ 0.1 pc) and of high density (≳105 cm-3) and thus are highly probable candidates for protostellar condensations just before star formation. The striking feature of these starless compact condensations is the steep slope of the mass spectrum (dN/dM ~ M-2.5 for 3.5 M☉ < M < 20.1 M☉). Under the assumption of uniform star formation efficiency, the spectrum resembles the stellar initial mass function (IMF) for a mass of ≲a few solar masses. This suggests that the stellar IMF is the result of the fragmentation process from relatively lower density cores. The statistical analysis of the starless condensations yields the lifetime of the condensations of ~4 × 105 yr, which is several times longer than free-fall timescale. This short timescale compared with magnetic flux loss time may indicate that the timescale is determined by the dissipation timescale of turbulence.