Mid-Infrared Spectroscopy of Carbon Stars in the Small Magellanic Cloud
Mid-Infrared Spectroscopy of Carbon Stars in the Small Magellanic Cloud
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DOI：
10.1086/504516
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发表时间：
2006-03
期刊：
影响因子：
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通讯作者：
G. Sloan;K. Kraemer;M. Matsuura;M. Matsuura;P. R. Wood;Stephan D. Price;M. Egan
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文献类型：
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作者：
G. Sloan;K. Kraemer;M. Matsuura;M. Matsuura;P. R. Wood;Stephan D. Price;M. Egan
我们利用斯皮策太空望远镜上的红外光谱仪对小麦哲伦星云（SMC）中的36个天体进行了观测。其中19个是碳星。对近红外和中红外光度法的检查表明，富碳和富氧尘埃源遵循两个容易分离的序列。将SMC中的19颗碳星的光谱与银河系中碳星的红外空间天文台（ISO）的光谱进行比较，发现了显著的差异。SMC样品中C2H2在7.5和13.7 μm处的吸收谱带较强，而SiC粉尘在11.3 μm处的发射谱带较弱。我们在26-30 μm处测量的MgS尘埃发射特征不太确定，但这种特征在SMC样品中似乎也较弱。所有这些结果都与SMC中较低的金属丰度一致。SMC中较低丰度的SiC颗粒可能导致低效率的富碳尘埃产生，这可以解释光谱中看到的过量C2H2气体。SMC中SiC粉尘发射最强的源比样品中其他源具有更红的红外颜色，这意味着更多的非晶态碳，它们也往往表现出更强的mg粉尘发射。最弱的SiC发射特征倾向于向蓝色偏移；这些光谱可能来自具有大SiC晶粒的低密度壳体。
We have observed a sample of 36 objects in the Small Magellanic Cloud (SMC) with the Infrared Spectrometer on the Spitzer Space Telescope. Nineteen of these sources are carbon stars. An examination of the near- and mid-infrared photometry shows that the carbon-rich and oxygen-rich dust sources follow two easily separated sequences. A comparison of the spectra of the 19 carbon stars in the SMC to spectra from the Infrared Space Observatory (ISO) of carbon stars in the Galaxy reveals significant differences. The absorption bands at 7.5 and 13.7 μm due to C2H2 are stronger in the SMC sample, and the SiC dust emission feature at 11.3 μm is weaker. Our measurements of the MgS dust emission feature at 26-30 μm are less conclusive, but this feature appears to be weaker in the SMC sample as well. All of these results are consistent with the lower metallicity in the SMC. The lower abundance of SiC grains in the SMC may result in less efficient carbon-rich dust production, which could explain the excess C2H2 gas seen in the spectra. The sources in the SMC with the strongest SiC dust emission tend to have redder infrared colors than the other sources in the sample, which implies more amorphous carbon, and they also tend to show stronger MgS dust emission. The weakest SiC emission features tend to be shifted to the blue; these spectra may arise from low-density shells with large SiC grains.