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arXiv 0901.4207astro-ph.GAastro-ph.SR
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从尘埃柱密度数据导出的核心质量函数的保真度

On the fidelity of the core mass functions derived from dust column density data

J. Kainulainen, C. J. Lada, J. M. Rathborne, J. F. Alves

备注：
9 pages, 6 figures, accepted for publication in A&A
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摘要：

目的：我们研究的可恢复性和完整性限制的致密的核心质量函数（CMFs）来自分子云消光数据和核心识别计划的基础上，二维阈值。研究方法：我们进行了模拟，其中一个人口的人工核心嵌入到可变的背景消光场的烟斗星云。我们从模拟的消光图中提取核心，构建CMF，并将它们与输入CMF进行比较。重复使用各种提取参数和几个核心人口与不同的输入质量函数和不同程度的拥挤的模拟。结果：所观察到的CMF的保真度取决于为我们的背景的核心提取算法所选择的参数。更重要的是，这取决于核心人口的拥挤程度。我们发现，当核的平均间距大于核的平均直径（f>1）时，观测到的CMF可靠地恢复了真实的CMF。如果这一条件成立，则在M > 0.8-1.5 Msun以上导出的CMF是准确和完整的，这取决于用于岩心提取的参数。在模拟中，最好的保真度与1或2倍的检测阈值的均方根噪声的消光数据，并与3倍的均方根噪声的轮廓水平间距。选择更大的阈值和更宽的水平间距增加了极限质量。模拟表明，当f>1.5时，单个核心的质量以25- 30%的典型不确定性恢复。当f=1时，不确定度约为60%。在f<1的非常拥挤的情况下，核心识别算法无法充分恢复核心的质量。对于烟斗星云的核心，f~2.0，因此在该区域使用该方法是合理的。

英文摘要：

Aims: We examine the recoverability and completeness limits of the dense core mass functions (CMFs) derived for a molecular cloud using extinction data and a core identification scheme based on two-dimensional thresholding. Methods: We performed simulations where a population of artificial cores was embedded into the variable background extinction field of the Pipe nebula. We extracted the cores from the simulated extinction maps, constructed the CMFs, and compared them to the input CMFs. The simulations were repeated using a variety of extraction parameters and several core populations with differing input mass functions and differing degrees of crowding. Results: The fidelity of the observed CMF depends on the parameters selected for the core extraction algorithm for our background. More importantly, it depends on how crowded the core population is. We find that the observed CMF recovers the true CMF reliably when the mean separation of cores is larger than their mean diameter (f>1). If this condition holds, the derived CMF is accurate and complete above M > 0.8-1.5 Msun, depending on the parameters used for the core extraction. In the simulations, the best fidelity was achieved with the detection threshold of 1 or 2 times the rms-noise of the extinction data, and with the contour level spacings of 3 times the rms-noise. Choosing larger threshold and wider level spacings increases the limiting mass. The simulations show that when f>1.5, the masses of individual cores are recovered with a typical uncertainty of 25-30 %. When f=1 the uncertainty is ~60 %. In very crowded cases where f<1 the core identification algorithm is unable to recover the masses of the cores adequately. For the cores of the Pipe nebula f~2.0 and therefore the use of the method in that region is justified.

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