Infrared absorption band at 7 mum of protostar dusts- An explanation with magnesium

原恒星尘埃 7 微米处的红外吸收带——镁的解释

• 批准号: 07804014
• 负责人: WADA Setsuko
• 金额: $ 1.22万
• 依托单位: The University of Electro-Gommunications
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07804014/
• 关键词: Interstellar Dust; Circumstellar Dust; Infrared Absorption Spectrum; Car bonate; Dark Cloud; Protostar; 赤外線スペクトル; 塵

An infrared absorption band at a wavelength of 7 mum was observed in embedded protostars. Differences of the band width are seen in these objects. Up to now, various materials are proposed to the origin of the band, i.e., hydrocarbons, methanol, photolyzed mixtures of CO_2, H_2, NH_3 etc, and carbonates. We examined again infrared absorption bands of carbonate materials, pure carbonate, and mixtures of carbonate with oxides and hydroxides.Pure MgCO_3 and FeCO_3 show a peak at 6.83-6.85mum and 6.93-6.94mum, respectively. The features are very similar tothe 7 mum band shape observed in W33A,however these carbonates show additional subpeaks around 11mum region, which have not observed in protostars.We synthesized carbonate-oxide-hydroxide mixtures by (1) grinding oxides in CO_2 atmosphere, and (2) heating of magnesium carbonate hydroxide under vacuum. The products show a very broad band around 7 mum which is matched to the band observed in Mon R2 #2. In addition, the peak height of the subpeaks around 11mum of these materialsare very small.The main result is summarized as follows. Carbonates are good candidates for the 7 mum band of protostars though their spectra have some additional bands.

在嵌入的原恒星中观察到波长为 7 μm 的红外吸收带。在这些物体中可以看到带宽的差异。迄今为止，人们提出了多种材料作为能带的来源，即碳氢化合物、甲醇、CO_2、H_2、NH_3等的光解混合物以及碳酸盐。我们再次检测了碳酸盐材料、纯碳酸盐以及碳酸盐与氧化物和氢氧化物的混合物的红外吸收带。纯MgCO_3和FeCO_3分别在6.83-6.85mum和6.93-6.94mum处显示出峰值。这些特征与在 W33A 中观察到的 7 mum 带形状非常相似，但是这些碳酸盐在 11mum 区域附近显示出额外的亚峰，这在原恒星中没有观察到。我们通过 (1) 在 CO_2 气氛中研磨氧化物来合成碳酸盐-氧化物-氢氧化物混合物，并(2)在真空下加热氢氧化碳酸镁。产品在 7 mum 附近显示出非常宽的谱带，与 Mon R2 #2 中观察到的谱带相匹配。此外，这些材料的11μm附近的次峰峰高非常小。主要结果总结如下。碳酸盐是原恒星 7 母带的良好候选者，尽管它们的光谱有一些额外的带。