FORMALDEHYDE DENSITOMETRY OF STARBURST GALAXIES: DENSITY-INDEPENDENT GLOBAL STAR FORMATION
FORMALDEHYDE DENSITOMETRY OF STARBURST GALAXIES: DENSITY-INDEPENDENT GLOBAL STAR FORMATION
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DOI：
10.1088/0004-637x/766/2/108
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发表时间：
2013-02
期刊：
影响因子：
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通讯作者：
J. Mangum;J. Darling;C. Henkel;K. Menten
中科院分区：
文献类型：
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作者：
J. Mangum;J. Darling;C. Henkel;K. Menten
精确的技术，允许推导出的空间密度在星星形成区是罕见的。一种应用于推导银河系星星形成区空间密度的技术利用了甲醛（H2 CO）的K-二重态跃迁的密度敏感特性。本文是对我们在56个星爆样品中H_2CO的甲醛110-111（λ = 6.2cm）和211-212（λ = 2.1cm）K-二重态跃迁测量的一个扩展。我们已经扩大了星系的数量，在这两个过渡已被检测到从5到13。我们已经改进了我们的空间密度测量结合动力学温度的基础上NH3测量的11个星系，在我们的样本中共有14个速度分量。我们的空间密度测量值位于104.5到105.5 cm−3的相对较窄的范围内。这意味着LIR和Mdense之间的Schmidt-Kennicutt关系（1）是可用于形成恒星的致密气体质量库的指示，（2）在最明亮的星暴星系中，并不直接依赖于驱动星星形成过程的较高平均密度。我们还使用我们的H2 CO测量，以获得两个单独的措施，致密的气体质量一般较小，在许多情况下，由102-103的一个因素，比那些来自使用HCN。这种差异表明，在我们的星爆星系样本中，H2 CO追踪到了一个更致密、更紧凑的巨型分子云成分。我们还报告了与H2 CO 110-111测量同时进行的OH的旋转激发λ = 6.3 cm 2Π1/2 J = 1/2态和H111α无线电复合线的测量。
Accurate techniques that allow for the derivation of the spatial density in star formation regions are rare. A technique that has found application for the derivation of spatial densities in Galactic star formation regions utilizes the density-sensitive properties of the K-doublet transitions of formaldehyde (H2CO). In this paper, we present an extension of our survey of the formaldehyde 110–111 (λ = 6.2 cm) and 211–212 (λ = 2.1 cm) K-doublet transitions of H2CO in a sample of 56 starburst systems. We have extended the number of galaxies in which both transitions have been detected from 5 to 13. We have improved our spatial density measurements by incorporating kinetic temperatures based upon NH3 measurements of 11 of the galaxies with a total of 14 velocity components in our sample. Our spatial density measurements lie in a relatively narrow range from 104.5 to 105.5 cm−3. This implies that the Schmidt–Kennicutt relation between LIR and Mdense (1) is an indication of the dense gas mass reservoir available to form stars and (2) is not directly dependent upon a higher average density driving the star formation process in the most luminous starburst galaxies. We have also used our H2CO measurements to derive two separate measures of the dense gas mass which are generally smaller, in many cases by a factor of 102–103, than those derived using HCN. This disparity suggests that H2CO traces a denser, more compact component of the giant molecular clouds in our starburst galaxy sample. We also report measurements of the rotationally excited λ = 6.3 cm 2Π1/2J = 1/2 state of OH and the H111α radio recombination line taken concurrently with our H2CO 110–111 measurements.