RESOLVED MEASUREMENTS OF XCO IN NGC 6946
RESOLVED MEASUREMENTS OF XCO IN NGC 6946
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NGC 6946 中 XCO 的解析测量
DOI：
10.1088/0004-637x/744/1/42
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
N. Scoville
中科院分区：
文献类型：
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作者：
J. Donovan Meyer;J. Koda;R. Momose;M. Fukuhara;T. Mooney;S. Towers;F. Egusa;R. Kennicutt;N. Kuno;M. Carty;T. Sawada;N. Scoville
我们提出了迄今为止最大的样本的巨大分子云（GMCs）在一个实质性的螺旋星系以外的银河系。我们绘制了螺旋星系NGC 6946中心5 kpc区域内12 CO（J = 1-0）跃迁的分子气体分布图。通过结合野边山射电天文台45米单碟望远镜和毫米天文干涉仪研究组合阵列的观测，我们能够获得高图像保真度和精确测量LCO与以前的纯干涉研究相比。我们解决个别GMC，测量它们的光度和维里质量，并推导出XCO-转换因子CO测量到H2质量-在个别云。平均而言，我们发现XCO = 1.2 × 1020 cm−2（K km s−1）−1，这在我们的不确定性范围内与先前推导出的银河系值以及我们推导出的银河系GMC高于我们的质量敏感性极限的值一致。我们的GMC的性质在很大程度上与在银河系盘中检测到的分子云的趋势一致，除了在NGC 6946中心的1000 pc范围内检测到的6个云，它们在给定的大小和光度下表现出更大的速度色散，就像在银河系中心观察到的那样。
We present the largest sample to date of giant molecular clouds (GMCs) in a substantial spiral galaxy other than the Milky Way. We map the distribution of molecular gas with high resolution and image fidelity within the central 5 kpc of the spiral galaxy NGC 6946 in the 12CO (J = 1–0) transition. By combining observations from the Nobeyama Radio Observatory 45 m single dish telescope and the Combined Array for Research in Millimeter Astronomy interferometer, we are able to obtain high image fidelity and accurate measurements of LCO compared with previous purely interferometric studies. We resolve individual GMCs, measure their luminosities and virial masses, and derive XCO—the conversion factor from CO measurements to H2 masses—within individual clouds. On average, we find that XCO = 1.2 × 1020 cm−2 (K km s−1)−1, which is consistent within our uncertainties with previously derived Galactic values as well as the value we derive for Galactic GMCs above our mass sensitivity limit. The properties of our GMCs are largely consistent with the trends observed for molecular clouds detected in the Milky Way disk, with the exception of six clouds detected within ∼400 pc of the center of NGC 6946, which exhibit larger velocity dispersions for a given size and luminosity, as has also been observed at the Galactic center.