Understanding star formation in molecular clouds - I. Effects of line-of-sight contamination on the column density structure
Understanding star formation in molecular clouds - I. Effects of line-of-sight contamination on the column density structure
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了解分子云中的恒星形成 - I 视线污染对柱密度结构的影响
DOI：
10.1051/0004-6361/201423569
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发表时间：
2015
影响因子：
6.5
通讯作者：
Federrath
中科院分区：
文献类型：
--
作者：
Schneider N;Ossenkopf V;Csengeri T;Klessen;Federrath
我们分析了来自赫歇尔尘埃连续观测的一个样本的突出，大规模的红外暗云（IRDC），即G11.11-0.12，G18.82-0.28，G28.37+0.07，和G28.53-0.25的柱密度和温度图。利用13 CO 1→0和12 CO 3→2资料对云的速度结构进行了解析，结果表明，这些IRDC是大质量巨分子云中的密集区，而不是孤立的特征。所有云的柱密度的概率分布函数（PDF）在所有（高）柱密度上都有幂律分布，与云的演化阶段无关：G11.11-0.12、G18.82-0.28和G28.37+0.07包含（原）星，而G28.53-0.25没有显示出星星形成的迹象。这与近红外和/或中红外消光图报告的纯对数正态PDF相反。如果我们对嵌入IRDC的整个GMC的柱密度图进行PDF分析，我们只会发现低柱密度的对数正态分布。通过比较PDF斜率和径向柱密度分布的三个我们的云，我们属性的幂律的影响，大规模的引力坍缩和本地自由落体崩溃的前和原恒星的核心最高的柱密度。辐射反馈不太可能对云的性质产生重大影响，因为云大多没有形成星星。独立于PDF分析，我们发现12 CO的光谱轮廓G28.37+0.07和G11.11-0.12的下降签名，支持引力坍缩的情况。我们的研究结果与早期的解释一致，认为大质量IRDC是GMC内的致密区域，可能是大质量恒星或星团的祖先。至少有一些IRDC可能与脊（在小面积上N> 1023 cm-2的高柱密度区域）具有相同的特征，这是为附近的IR亮GMC定义的。由于IRDC仅限于湍流（重力主导）云区域，因此从这种裁剪图像构建的PDF并不代表（湍流主导）低柱密度云区域。
We analyse column density and temperature maps derived fromHerscheldust continuum observations of a sample of prominent, massive infrared dark clouds (IRDCs) i.e. G11.11-0.12, G18.82-0.28, G28.37+0.07, and G28.53-0.25. We disentangle the velocity structure of the clouds using13CO 1→0 and12CO 3→2 data, showing that these IRDCs are the densest regions in massive giant molecular clouds (GMCs) and not isolated features. The probability distribution function (PDF) of column densities for all clouds have a power-law distribution over all (high) column densities, regardless of the evolutionary stage of the cloud: G11.11-0.12, G18.82-0.28, and G28.37+0.07 contain (proto)-stars, while G28.53-0.25 shows no signs of star formation. This is in contrast to the purely log-normal PDFs reported for near and/or mid-IR extinction maps. We only find a log-normal distribution for lower column densities, if we perform PDFs of the column density maps of thewholeGMC in which the IRDCs are embedded. By comparing the PDF slope and the radial column density profile of three of our clouds, we attribute the power law to the effect of large-scale gravitational collapse and to local free-fall collapse of pre- and protostellar cores for the highest column densities. A significant impact on the cloud properties from radiative feedback is unlikely because the clouds are mostly devoid of star formation. Independent from the PDF analysis, we find infall signatures in the spectral profiles of12CO for G28.37+0.07 and G11.11-0.12, supporting the scenario of gravitational collapse. Our results are in line with earlier interpretations that see massive IRDCs as the densest regions within GMCs, which may be the progenitors of massive stars or clusters. At least some of the IRDCs are probably the same features asridges(high column density regions withN> 1023cm-2over small areas), which were defined for nearby IR-bright GMCs. Because IRDCs are only confined to the densest (gravity dominated) cloud regions, the PDF constructed from this kind of a clipped image does not represent the (turbulence dominated) low column density regime of the cloud.
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DOI：
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发表时间：
2014
期刊：
影响因子：
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1998
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作者：
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DOI：
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发表时间：
2008
期刊：
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作者：
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