KMS of Xinjiang Astronomical Observatory, CAS
| 大质量恒星形成区有机分子的化学建模和化学演化研究 | |
| Alternative Title | Study on Chemical Simulation of Organic Molecules and Chemical Evolution in High Mass Star-formation region |
李润霞
| |
| Subtype | 硕士 |
| Thesis Advisor | 周建军 |
| 2020 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Degree Name | 理学硕士 |
| Degree Discipline | 天体物理 |
| Keyword | 天体化学,丰度,恒星形成 |
| Abstract | 随着射电天文望远镜分辨率和灵敏度的不断提升，人们已经探测到了许多 星际分子。我们想要根据星际物理环境的不同来研究它们的化学演化过程，同时 恒星形成过程中往往伴随着丰富的物理和化学变化，在不同的天体演化阶段，星 际分子的分度也是有所不同的，所以我们可以通过天文观测对星际环境中的分 子丰度进行分析研究，进而来判断恒星形成不同的演化阶段。在这里主要选取 了氤胺(NH2CN )和它的同分异构体碳化二亚胺(HNCNH)进行化学模型的研究 来了解它们在星际环境中的形成和消耗情况，以及N2H+ (1-0)、H13CO+ (1-0)、 HCN(1-0)和HN13C (1-0)数据进行处理和分析，进而找到可以示踪大质量恒星形 成演化阶段的星际分子。在对HNCNH和NH2CN两个星际分子进行星际介质中的化学模拟过程中, 我们主要采用基于速率方程的气粒模拟方法对HNCNH和NH2CN的化学模型进 行了研究。根据初始元素丰度、辐射强度、系统温度、宇宙线电离率等外 部参数，可以得到HNCNH和NH2CN主要化学物质丰度随时间演化的曲线。我 们研究了在不同物理条件下的HNCNH和NH2CN化学模型，研究表明所建立的 升温模型中初始密度nH=2 x 104cm-3和宇宙线电离率1.3 x 10-17s-1的模拟结果 与观测结果吻合的较好。该模型有助于对NH2CN和HNCNH在星际介质环境下化学机理的理解。 在对前生命分子HNCNH和NH2CN分子的化学模型研究的过程中发现 HCO+、HCN、HNC和N2H+等小分子和离子对于HNCNH和NH2CN分子的形 成和演化有重要的影响，所以我们挑选了 N2H+ (1-0)、H13CO+ (1-0)、HCN(1-0) 和HN13C (1-0)数据来研究大质量恒星形成团的化学性质和演化。研究结果表明 H13CO+和HN13C的丰度受H2柱密度的影响。由于这两个丰度的中位数从A阶 段到B阶段增加了将近10倍，H13CO+和HN13C适合于追踪大质量恒星形成团 块的演化。从A阶段到B阶段，四种分子丰度的增长从高到低依次为H13CO+、 HCN、HN13C和N2H+。最终的结果表明，用高角度分辨率观测光学薄分子更有 利于研究大质量恒星形成团块的化学演化。 |
| Other Abstract | With the continuous improvement of the resolution and sensitivity of radio tele scopes, many interstellar molecules have been detected. We want to study their chem ical evolution according to different interstellar physical environments. At the same time, the process of star formation is often accompanied by rich physical and chemi cal changes, and the degrees of interstellar molecules are different in different stages of celestial evolution. therefore, we can analyze and study the molecular abundance in the interstellar environment through astronomical observation and then to judge the different evolution stages of star formation. Here, NH2CN and its isomer HNCNH are selected to study the chemical model to understand their formation and consumption in the interstellar environment, and the data of N2H+(1-0), H13CO+(1-0), HCN (1-0) and HN13C(1-0) are processed and analyzed. then we can find the interstellar molecules that can trace the formation and evolution of high-mass stars. In the process of chemical simulation of two interstellar molecules, HNCNH and NH2CN in interstellar medium. We use the gas-particle simulation method based on the rate equation to study the chemical models of HNCNH and NH2CN. According to the external parameters such as initial element abundance, radiation intensity, system temperature and cosmic ray ionization rate, the time evolution curves of the main chemical substance abundances of HNCNH and NH2CN can be obtained. We have studied the chemical models of HNCNH and NH2CN under different physical conditions. The results show that the simulation results of initial density nH=2 x 104cm-3 and the cosmic ray ionization rate 1.3 x 10-17s-1 in the warm-up model are in agreement with the observed values. The models can be used to help with the understanding of chemical reaction mechanism of NH2CN and HNCNH under interstellar conditions. In the chemical modeling of prebiotic HNCNH and NH2CN, we found that small molecules and ions such as HCO+, HCN, HNC and N2H+have important effects on the formation and evolution of HNCNH and NH2CN molecules. So we selected N2H+(1- 0), H13CO+(1-0), HCN (1-0) and HN13C(1-0) data to study the chemical properties and evolution of massive star forming clusters. The results show that the abundance of H13CO+and HN13C is affected by the column density of H2. Since the median of these two abundances increases nearly tenfold from stage A to stage B, H13CO+and HN13C are suitable for tracking the evolution of massive star clumps. Stages A to stage B have increased nearly tenfold, and H13CO+ and HN13C are suitable for tracking the evolution of massive star-forming clumps. From stage A to stage B, the growth of four molecular abundances from high to low is H13CO+, HCN, HN13C and N2H+. The final results show that the observation of optical thin molecules with high angular resolution is more helpful to study the chemical evolution of massive star clumps. |
| Pages | 48 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xao.ac.cn/handle/45760611-7/4138 |
| Collection | 研究生学位论文 |
| Affiliation | 中国科学院新疆天文台 |
| First Author Affilication | Xinjiang Astronomical Observatory, Chinese Academy of Sciences |
| Recommended Citation GB/T 7714 | 李润霞. 大质量恒星形成区有机分子的化学建模和化学演化研究[D]. 北京. 中国科学院大学,2020. |
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| 李润霞.pdf（13851KB） | 学位论文 | 暂不开放 | CC BY-NC-SA | Application Full Text | ||
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