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arXiv 1004.0398astro-ph.GA
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大质量致密团块的性质：HCN和CS的测绘

The Properties of Massive, Dense, Clumps: Mapping Surveys of HCN and CS

Jingwen Wu, Neal Evans, Yancy Shirley, Claudia Knez

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105 pages, 48 figures, 16 tables. To appear in ApJS; Add references for section 5.
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摘要：

我们已经绘制了50多个大规模的，致密的团块与四个致密气体示踪剂：HCN J=1-0和3-2;和CS J=2-1和7-6转换。光学薄的H^{13}CN 3-2和C^{34}S 5-4的谱线也朝向地图中心。这些图通常在我们的分辨率下显示单峰分布，即使J跃迁更高。从每个过渡的等高线图计算尺寸、维里质量、表面密度和明确定义的角尺寸（FWHM）内的平均体积密度。我们发现，具有更高的有效密度的过渡通常跟踪更紧凑，内部的团块，但有更大的线宽，导致使用不同的示踪剂的反线宽尺寸关系。CS 2-1、HCN 1-0、HCN 3-2和CS 7-6的平均表面密度分别为0.29、0.33、0.78和1.09 g cm^{-2}。我们发现L_{IR}与表面密度没有相关性，而与平均体积密度可能呈负相关，这与一些理论预期相反。我们在数据中没有看到模拟者提出的L '_{mol}和平均密度之间关系的证据。对于每一种稠密气体示踪剂，L '_{mol}与维里质量的相关性大致为线性。对于这些大质量的致密团块，发现红外光度和所有致密气体示踪剂的线光度之间几乎呈线性相关，光度的下限为L_{IR} =10^{4.5} Lsun。L_{IR} -L '_{HCN 1 -0}关联与星系中的关联符合得很好。这些相关性表明，当测量致密气体的质量时，从致密团块的尺度到遥远星系的尺度，每单位质量的恒星形成率是恒定的。这些结果支持了这样的建议，即星暴星系可以被理解为具有大部分气体的致密团块。

英文摘要：

We have mapped over 50 massive, dense clumps with four dense gas tracers: HCN J=1-0 and 3-2; and CS J=2-1 and 7-6 transitions. Spectral lines of optically thin H^{13}CN 3-2 and C^{34}S 5-4 were also obtained towards the map centers. These maps usually demonstrate single well-peaked distributions at our resolution, even with higher J transitions. The size, virial mass, surface density, and mean volume density within a well-defined angular size (FWHM) were calculated from the contour maps for each transition. We found that transitions with higher effective density usually trace the more compact, inner part of the clumps but have larger linewidths, leading to an inverse linewidth-size relation using different tracers. The mean surface densities are 0.29, 0.33, 0.78, 1.09 g cm^{-2} within FWHM contours of CS 2-1, HCN 1-0, HCN 3-2 and CS 7-6, respectively. We find no correlation of L_{IR} with surface density and a possible inverse correlation with mean volume density, contrary to some theoretical expectations. We see no evidence in the data for the relation between L'_{mol} and mean density posited by modelers. The correlation between L'_{mol} and the virial mass is roughly linear for each dense gas tracer. A nearly linear correlation was found between the infrared luminosity and the line luminosity of all dense gas tracers for these massive, dense clumps, with a lower cutoff in luminosity at L_{IR}=10^{4.5} Lsun. The L_{IR}-L'_{HCN1-0} correlation agrees well with the one found in galaxies. These correlations indicate a constant star formation rate per unit mass from the scale of dense clumps to that of distant galaxies when the mass is measured for dense gas. These results support the suggestion that starburst galaxies may be understood as having a large fraction of gas in dense clumps.

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