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arXiv 0908.3586astro-ph.CO
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附近星系中心的CI和CO。星暴星系NGC 278、NGC 660、NGC 3628、NGC 4631和NGC 4666

CI and CO in nearby galaxy centers. The star-burst galaxies NGC 278, NGC 660, NGC 3628, NGC 4631, and NGC 4666

F. P. Israel

备注：
Accepted for publication in Astronomy & Astrophysics
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摘要：

NGC 278、NGC 660、NGC 3628、NGC 4631和NGC 4666的J= 1 - 0、J = 2 - 1、J =3-2、J=4-3 ~（12）CO、J=1-0、J=2-1和J=3-2 ~（13）CO中心角分平方线的地图和测量，以及其中三个的492 GHz [CI]地图，都被用来模拟分子气体。所有五个天体都在内部区域表现出明亮的CO发射，在NGC 660，NGC 3628和NGC 4666中具有较强的中心浓度，但在最弱的CO发射体NGC 278和NGC 4631中没有。在所有情况下，观察到的线可以被建模，只有至少两个不同的气体成分。分子气体的物理条件被发现是不同的星系星系。相对稀薄（密度100-1000 cm-3）和高动力学温度（100-150 K）的气体存在于所有星系中，可能除了NGC 3628，并与较冷（10-30 K）和较密（3000-10000 cm-3）的气体混合。在所有星系中心，CO到H2的转换因子X通常比太阳邻域的“标准”值小一个数量级。分子气体被限制在距离原子核0.6至1.5 kpc的半径内。在这些半径范围内，H2的质量通常为0.6-1.5 × 10**8 M（O），相当于同一区域内动力学质量的百分之几。

英文摘要：

Maps and measurements of the J=1-0, J=2-1, J=3-2, J=4-3 12CO, the J=1-0, J=2-1 and J=3-2 13CO lines in the central arcminute squared of NGC 278, NGC 660, NGC 3628, NGC 4631, and NGC 4666, as well as 492 GHz [CI] maps in three of these are used to model the molecular gas. All five objects exhibit bright CO emission in the inner regions, with strong central concentrations in NGC 660, NGC 3628, and NGC 4666, but not in the weakest CO emitters NGC 278 and NGC 4631. In all cases, the observed lines could be modeled only with at least two distinct gas components. The physical condition of the molecular gas is found to differ from galaxy to galaxy. Relatively tenuous (density 100-1000 cm-3) and high kinetic temperature (100-150 K) gas occurs in all galaxies, except perhaps NGC 3628, and is mixed with cooler (10-30 K) and denser (3000-10000 cm-3) gas. In all galaxy centers, the CO-to-H2 conversion factor X is typically an order of magnitude smaller than the `standard' value for the Solar Neighborhood. The molecular gas is constrained within radii between 0.6 and 1.5 kpc from the nuclei. Within these radii, H2 masses are typically 0.6-1.5 x 10**8 M(O), which corresponds to no more than a few per cent of the dynamical mass in the same region.

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