Origins of Molecular Clouds in Early-type Galaxies
Origins of Molecular Clouds in Early-type Galaxies
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DOI：
10.3847/1538-4357/ab54ce
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发表时间：
2018-10
期刊：
影响因子：
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通讯作者：
I. Babyk;I. Babyk;B. McNamara;B. McNamara;P. Tamhane;P. Nulsen;P. Nulsen;H. Russell;A. Edge
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文献类型：
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作者：
I. Babyk;I. Babyk;B. McNamara;B. McNamara;P. Tamhane;P. Nulsen;P. Nulsen;H. Russell;A. Edge
我们分析了钱德拉对 40 个早期螺旋星系和椭圆星系热大气的观测结果。使用新的温度、密度、冷却时间和质量分布，我们探索了它们的热大气和冷分子气体之间的关系。从星团中的中央星系到正常的巨型椭圆星系和早期螺旋星系，分子气体质量与四十年来大气气体质量和密度相关。质量和密度关系分别遵循幂律： 和 ，在 10 kpc 时。对于早期型星系，10kpc半径内的分子气体与大气气体的比率在3%到10%之间，对于星团中的中心星系，分子气体与大气气体的比率在3%到50%之间。当早期型星系的大气冷却时间在 10 kpc 半径处低于 ∼1 Gyr 时，其分子气体水平可被检测到。在中央星团星系中也发现了类似的趋势。我们发现冷却时间与自由落体时间之比 tc/tff 与早期型星系中分子云的存在或不存在之间没有关系。这些数据与早期星系中由热大气凝结而成的大部分分子气体一致。
We analyze Chandra observations of the hot atmospheres of 40 early spiral and elliptical galaxies. Using new temperature, density, cooling time, and mass profiles, we explore relationships between their hot atmospheres and cold molecular gas. Molecular gas mass correlates with atmospheric gas mass and density over four decades from central galaxies in clusters to normal giant ellipticals and early spirals. The mass and density relations follow power laws: and , respectively, at 10 kpc. The ratio of molecular gas to atmospheric gas within a 10 kpc radius lies between 3% and 10% for early-type galaxies and between 3% and 50% for central galaxies in clusters. Early-type galaxies have detectable levels of molecular gas when their atmospheric cooling times fall below ∼1 Gyr at a radius of 10 kpc. A similar trend is found in central cluster galaxies. We find no relationship between the ratio of the cooling time to free-fall time, tc/tff, and the presence or absence of molecular clouds in early-type galaxies. The data are consistent with much of the molecular gas in early-type galaxies having condensed from their hot atmospheres.