在原星中观察分离的CO2和CO2冰
N G C Brunken1, A C A Boogert2, E F van Dishoeck3,1
1Leiden Observatory, 2300 RA Leiden, The Netherlands.
概括
星际二氧化碳冰的加热会导致分离,形成二氧化碳甲醇混合物. 同位素比表明冰形成和加热阶段的最小分化,为原恒星进化提供了洞察力.
科学领域:
- 天体化学
- 星际介质物理
- 原星的演化
背景情况:
- 星际冰的演变取决于它们的化学和热环境.
- 二氧化碳 (CO2) 冰的振动模式作为热跟踪器.
- 詹姆斯·韦伯太空望远镜 (JWST) 可以详细观察二氧化碳冰的特征.
研究的目的:
- 在高质量 (IRAS 20126) 和低质量 (Per-emb 35) 原星中分析二氧化碳冰的振动模式.
- 研究冰的加热和分离对二氧化碳冰的组成的影响.
- 确定二氧化碳冰中的同位素比例 (12C/13C) 并评估分化.
主要方法:
- 在近红外和中红外对二氧化碳冰的光谱观测.
- 对12CO2和13CO2的15.2微米曲,4.39微米拉伸和2.70微米组合模式的分析.
- 对振动模式进行一致的配置分解,以模拟冰混合.
主要成果:
- 观察到纯二氧化碳冰的特征性双峰和13CO2和12CO2的短波长峰.
- 由二氧化碳与CH3OH和H2O混合而成的一致的CO2冰形状,表明加热时的分离.
- 对于12CO2和13CO2的CO2成分的类似贡献表明最小的同位素分离.
- 在IRAS 20126中得出的12C/13C_ice=90±9比之前报告的气态CO低.
- 检测到纯CO2冰的13CO2曲模式在15.64μm.
结论:
- 在加热时,二氧化碳冰从富含水分层中分离出来,有利于CO2-CH3OH混合物.
- 通过形成和加热,二氧化碳冰的同位素比保持一致,这意味着有限的分化.
- 在IRAS 20126中得出的12C/13C比率为原恒星化学进化提供了新的约束.
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