Dense Molecular Gas in the Nearby Low-metallicity Dwarf Starburst Galaxy IC 10
Dense Molecular Gas in the Nearby Low-metallicity Dwarf Starburst Galaxy IC 10
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DOI：
10.3847/1538-4357/aacaf4
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发表时间：
2018-06
期刊：
影响因子：
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通讯作者：
A. Kepley;L. Bittle;A. Leroy;M. Jiménez-Donaire;A. Schruba;F. Bigiel;M. Gallagher;Kelsey E. Johnson;A. Usero
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文献类型：
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作者：
A. Kepley;L. Bittle;A. Leroy;M. Jiménez-Donaire;A. Schruba;F. Bigiel;M. Gallagher;Kelsey E. Johnson;A. Usero
星系中致密的分子气体和星星的形成是相互关联的。低金属丰度对这种关系的影响对于解释高红移星系的观测至关重要，高红移星系的金属丰度比今天的星系低。然而，它仍然相对未被探索，因为密集的分子气体示踪剂，如HCN和HCO+在低金属含量系统中是微弱的。本文介绍了绿色银行望远镜在低金属丰度（）星暴IC 10附近的巨分子云（34 pc）尺度上对HCN（1-0）和HCO+（1-0）的观测结果，并与其它星系的观测结果进行了比较。我们分别在五个点中的一个和三个点中检测到HCN和HCO+。这些值在其他星系中所见的范围内，但与其他低金属量来源和星暴中所见的最相似。检测遵循基准与关系.这些趋势表明，HCN和HCO+可以用来跟踪致密的分子气体在金属丰度的1/4 Z，到一级。致密气体的比例与螺旋星系相似，但低于U/LIRGs。致密分子气体星星的形成效率，但是，是在正常星系的上端和U/LIRGs一致。这些结果表明，CO和HCN/HCO+排放占据相同的相对体积，因为它们在更高的金属丰度，但整个发射结构的尺寸减小。对于高红移星系的致密气体质量估计可能需要对这种效应进行修正。
Dense molecular gas and star formation are correlated in galaxies. The effect of low metallicity on this relationship is crucial for interpreting observations of high-redshift galaxies, which have lower metallicities than galaxies today. However, it remains relatively unexplored because dense molecular gas tracers like HCN and HCO+ are faint in low-metallicity systems. We present Green Bank Telescope observations of HCN(1–0) and HCO+(1–0) on giant molecular cloud (34 pc) scales in the nearby low-metallicity ( ) starburst IC 10 and compare them to those in other galaxies. We detect HCN and HCO+ in one and three of five pointings, respectively. The values are within the range seen in other galaxies, but are most similar to those seen in other low-metallicity sources and in starbursts. The detections follow the fiducial – and – relationships. These trends suggest that HCN and HCO+ can be used to trace dense molecular gas at metallicities of 1/4 Z⊙, to first order. The dense gas fraction is similar to that in spiral galaxies, but lower than that in U/LIRGs. The dense molecular gas star formation efficiency, however, is on the upper end of those in normal galaxies and consistent with those in U/LIRGs. These results suggest that the CO and HCN/HCO+ emission occupy the same relative volumes as they do at higher metallicity, but that the entire emitting structure is reduced in size. Dense gas mass estimates for high-redshift galaxies may need to be corrected for this effect.