Molecular gas and star formation in the SAURON early-type galaxies
Molecular gas and star formation in the SAURON early-type galaxies
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DOI：
10.1111/j.1365-2966.2007.11759.x
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发表时间：
2007-03
影响因子：
4.8
通讯作者：
F. Combes;L. M. Young;L. M. Young;M. Bureau
中科院分区：
文献类型：
--
作者：
F. Combes;L. M. Young;L. M. Young;M. Bureau
本文介绍了用SAURON积分场摄谱仪对48个代表性E/S 0星系中的43个进行光学观测的CO辐射的测量结果。一氧化碳的检出率为12/43或28%，低于先前对早期类型的研究，但可能归因于不同的样本选择标准。正如预期的那样，早期类型，更明亮和质量更大的星系具有相对较低的分子气体含量。我们发现富CO星系比贫CO星系具有更高的Hβ，而更低的Fe 5015和Mgb吸收指数。这些趋势似乎主要是由恒星的年龄驱动的，这一假设得到了以下事实的支持：具有最强有力的星星形成证据的星系也是最富含CO的星系。事实上，来自当前样本的早期类型星系似乎扩展了远红外（FIR）光度，尘埃质量和其他星系类型分子质量之间众所周知的相关性。星星形成的解释也与SAURON星系的射电连续谱和远红外线通量比相一致，它们的星星形成效率与螺旋星系相似。因此，我们似乎已经确定了在早期星系中形成星星的物质，并证明了它正在积极地转变。然而，CO含量和大多数恒星参数之间缺乏强相关性，这与以下观点是一致的：在相当数量的样本星系中，分子气体是从外部吸积而来的，并且具有与旧的、预先存在的恒星成分相当独立的性质。
We present the results of a survey of CO emission in 43 of the 48 representative E/S0 galaxies observed in the optical with the SAURON integral-field spectrograph. The CO detection rate is 12/43 or 28 per cent. This is lower than previous studies of early-types but can probably be attributed to different sample selection criteria. As expected, earlier type, more luminous and massive galaxies have a relatively lower molecular gas content. We find that CO-rich galaxies tend to have higher Hβ but lower Fe5015 and Mgb absorption indices than CO-poor galaxies. Those trends appear primarily driven by the age of the stars, a hypothesis supported by the fact that the galaxies with the strongest evidence of star formation are also the most CO-rich. In fact, the early-type galaxies from the current sample appear to extend the well-known correlations between far-infrared (FIR) luminosity, dust mass and molecular mass of other galaxy types. The star formation interpretation is also consistent with the SAURON galaxies' radio continuum and FIR flux ratios, and their inferred star formation efficiencies are similar to those in spiral galaxies. It thus appears that we have identified the material fueling (residual) star formation in early-type galaxies, and have demonstrated that it is actively being transformed. Nevertheless, the lack of strong correlations between the CO content and most stellar parameters is compatible with the idea that, in a significant number of sample galaxies, the molecular gas has been accreted from the outside and has properties rather independent from the old, pre-existing stellar component.