KMS of Xinjiang Astronomical Observatory, CAS
| 天鹰座分子云中恒星形成区域的甲醛和 CO 观测 | |
| Alternative Title | H2CO and CO observations of star-forming regions in the Aquila molecular cloud |
KOMESH, TOKTARKHAN
| |
| Subtype | 博士 |
| Thesis Advisor | 加尔肯·叶生别克 |
| 2020-12-01 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Degree Name | 理学博士 |
| Degree Discipline | 天体物理 |
| Keyword | 星际分子 分子云 致密核 运动学与动力学 恒星形成 |
| Abstract | 理解和认识恒星形成过程对现代天体物理学至关重要。分子气体云在引力作用下坍塌形成致密核，并在致密核中形成恒星。近年来，对分子云的大量观测研究确定了分子云中恒星形成的物理条件和性质，揭示了恒星形成的大致过程。但是，至今仍有许多未解决的问题。特别是，恒星形成早期阶段的运动学和动力学性质还不清楚，恒星形成区周围环境如何影响恒星的形成还需要深入研究。天鹰座分子云 (AMC) 是穿过银河系银盘中央区域的宇宙尘埃暗条的一部分。分别为位于分子云西部的Serpens South（年轻嵌入式星团）和东部的W40（与HII区成协的星团）是两个有名的恒星形成区，它们是观测研究恒星形成的热点区域。 AMC中不同类型与演化阶段的恒星形成区域，为研究恒星形成的早期阶段与演化提供了很好的样本。本文利用H2CO吸收线和12CO同位素分布研究AMC中HII区和年轻嵌埋星团的结构形态，恒星形成区域和非恒星形成区域分子气体与星际尘埃之间的关系。为了在更小尺度上研究HII区，我们还使用Atacama Large Millimeter/submillimeter (ALMA) 干涉阵观测研究超致密（HC）HII区G345.01（HII区域演化第一阶段）。首先，我们使用新疆天文台南山26米射电望远镜对AMC做了大尺度的甲醛（H2CO（110-111））吸收线和氢射电复合线（H110α）成图观测。H2CO（110-111）吸收线的观测结果确定了受到Aquila分子云复合体中正在形成的恒星影响的区域及其动力学特性。H2CO的激发温度（Tex）的分布确定了两个已知的恒星形成区W40和Serpens South，一个新的较小恒星形成区Serpens 3。在接下来的工作中，我们在AMC中发现了称为光致离解区（PDRs）的区域。通过比较原恒星-星前核和不同区域的物理参数，研究选择性离解在恒星形成过程中的作用，恒星形成区域的演化时标与选择性离解的影响之间是否存在密切的关系。使用12CO，13CO和C18O（J = 1-0）谱线观测研究AMC中正在进行的恒星形成活动，使用70 µm和250 µm观测数据探测周围的物质，并作为核演化时标的指标。原恒星-星前核大多处于C18O柱密度最高的点，它们不断增加的演化时标与其所在位置的70µm / 250µm辐射强度比相关。 13CO /C18O丰度比（提供这些区域的离解速率）与70µm / 250µm的流量密度比（反映恒星形成活动的演化时标）相关。最后，我们使用ALMA对G345.01 HC H II区做了尘埃连续谱与分子谱线观测，以检验HC HII区应与旋转的热分子核相关的猜想。 我们使用SO2和CH3CN的高能跃迁寻找与3000 AU尺度上的旋转核一致的速度梯度。另外，我们探测到被氢复合线H29α示踪的电离气体。在假设局部热动平衡（LTE）与光薄的前提下，我们通过 population-diagram方法获得CH3CN旋转温度（Trot）与柱密度，通过G345.01 HC H II区中速度分布的特征发现，下落运动在该区域的气体运动学中起着主导作用。 |
| Other Abstract | An itemized understanding of the star forming process is important for modern astrophysics. Stars form from the gravitational collapse of molecular gas clouds. However, there are a number of open questions that explains and predicts how, where and why stars and their clusters form proves elusive. Recently, Large-scale and small-scale observations of molecular clouds have determined physical conditions and properties, and analyzed the process of star formation in molecular clouds. However, the kinematics and dynamics, especially in the early stages, are still not so clear. And how the surrounding environment affects star formation is still an open question.The Aquila molecular cloud (AMC) is part of a dark lane of cosmic dust flowing prominently through the central region of the galactic plane of the Milky Way. The two known sites of star formation – the western Serpens South, a young embedded cluster, and the eastern W40, a cluster associated with an H II region, become a hot spot for the study of star formation. As there are different types of star forming regions and different evalutionary stage of star formation the AMC is a good laboratory for studing the early stages of star formation in large scale.In this thesis, we study the morphology of the H II and the young embedded cluster in AMC using H 2 CO absorption line and 12 CO isotope distributions. We seek to understand the relationsip between the molecular gas and intelstellar dast in star-formation and non-star-formation regions. In order to stuty the H II region in small scale we also conduct observations toward the hyper-compact (HC) H II region (the first stage of development of H II region) G345.01 using the Atacama Large Millimeter/submillimeter Array (ALMA).First, in this work, we present the large-scale molecular line observations of the formaldehyde H 2 CO(1 10 − 1 11 ) absorption line and H110α radio recombination line in the AMC complex, using the Nanshan 25 m radio telescope. These first observations of the H 2 CO (1 10 − 1 11 ) absorption line determine the extent of the molecular regions that are affected by the ongoing star formation in the Aquila molecular complex and showIIIH 2 CO and CO observations of star-forming regions in the Aquila molecular cloud some of the dynamic properties. The distribution of the excitation temperature T ex for H 2 CO identifies the two known star formation regions W40 H II region and Serpens South as well as a smaller new region Serpens 3.Next, we encounter regions in the AMC that are called photo-dissociation regions (PDRs). We investigate the role of selective dissociation in the process of star formation by comparing the physical parameters of protostellar-prestellar cores and the distinct regions. We seek to understand whether there is a close relationship between the evolutionary age of star forming regions and the effect of selective dissociation. Weused wide-field observations of the 12 CO, 13 CO, and C 18 O ( J = 1 - 0) emission lines to study the ongoing star formation activity in the AMC, and used the 70 μm and 250 μm data to describe the heating of the surrounding material and as an indicator of the evolutionary age of the core. The protostellar-prestellar cores are found at locations with the highest C 18 O column densities and their increasing evolutionary age coincides with an increasing 70μm/250μm emission ratio at their location. The X 13 CO /X C 18 O ratio,which provides the dissociation rate for these regions correlates with the 70μm/250μm flux density ratio and reflects the evolutionary age of the star formation activity. In the third part, we observe G345.01 HC H II region in small scale. ALMA (Band 6, 256.3-259.6 GHz) dust continuum and molecular line observations were carried out. We aim to test a key prediction of this hypothesis, which is that HC H II regions should be associated with a rotating hot molecular core. We look for velocity gradients consistent with a rotating core on scales 3000 AU using high-energy transitions of SO 2 andCH 3 CN. We also observe the ionized gas emission traced by the H29α recombination line. The population-diagram method has been used to obtain the CH 3 CN rotation temperature (T rot ) and column density of the sources in our sample assuming LTE and low optical depths. The clear detection of the ‘central blue spot’signature of velocity distribution in G345.01 HC H II region indicates that infall motions play a fundamentalrole in the gas kinematics of this source. |
| Pages | 84 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xao.ac.cn/handle/45760611-7/4739 |
| Collection | 研究生学位论文 射电天文研究室 |
| 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 | KOMESH, TOKTARKHAN. 天鹰座分子云中恒星形成区域的甲醛和 CO 观测[D]. 北京. 中国科学院大学,2020. |
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| File Name/Size | DocType | Version | Access | License | ||
| TOKTARKHAN KOMESH.pd（4075KB） | 学位论文 | 暂不开放 | CC BY-NC-SA | Application Full Text | ||
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