宇宙不同空间尺度分子气体观测研究
发布时间：2018-08-15 11:59
【摘要】：氢的原子与分子冷气体广泛存在于恒星际空间(ISM),是恒星形成活动和星系演化过程中最直接的原料,通过对星系中冷气体观测研究,可以探索和理解天体物理的辐射机制,以及天体中的化学过程。近年来得益于观测设备,尤其是射电亚毫米波望远镜的技术进步,在不同尺度上,大量来自于不同分子、不同跃迁的分子谱线得以被探测和比较,伴随着恒星形成与星系演化的各种现象被发现,相关的物理解释方法、化学网络模型得以被构建,这使得人们对银河系中恒星形成、对星系演化的物理图景的理解得到了前所未有的更新。本论文是在这个背景下,为了更好地理解不同尺度上分子气体的性质,以及与恒星形成相关的物理现象,开展了几项前沿观测研究工作。这几项工作针对的空间尺度跨度很大,具体的科学目标也互有交叉： 我们首先对银河系的一些大质量恒星形成区(AFGL490、ON1、W33Main、G10.6-0.4,尺度约为0.1pc)进行了亚毫米波干涉仪(SMA)的高分辨率观测,研究了典型的碳链分子C2H的3-2跃迁,发现在较大尺度上C2H与致密的分子包层成协,但C2H的辐射峰值普遍与恒星形成区中心有偏移(约几万AU的尺度),而它的径向丰度分布与距离恒星形成区热核的距离有关,它在热核中心丰度较低,而在一些区域对应的分子包层中丰度较高。该工作结果与化学模型对C2H的化学性质的预测是符合的,而更高空间分辨率的数据可以帮助在更小尺度上对模型进行检验。这项工作既为将来进一步通过天体化学方法去理解分子气体与恒星形成,积累了重要的信息,也为我们把这种理解拓展到近邻星系提供了良好的参考。 我们研究的重点集中在近邻的恒星形成星系,使用亚毫米波望远镜(SMT)对一批富气体星系进行了CO2-1谱线观测(对应尺度约为1-10kpc)。我们的星系样本的特点在于目标源的恒星质量是中等偏低的(M*～108.5M& -1010.2M& ),并且母样本是由ALFALFA中性氢星表与WISE红外卫星星表交叉而得。我们结合多波段数据,分析比较了样本与AMIGA、COLDGASS巡天的异同,讨论了星系的分子气体质量(MH2)以及中性氢气体质量(MHI)与星系其他物理参数(恒星质量,NUV-r颜色以及红外颜色W3-W2等)的关系。结果显示1).在中低质量星系(M*≤1010M& )中,MHI/M*明显随着星系质量减小而升高,但MH2/M*几乎不变；2).我们引入了一个新的红外参数W3-W2,它在物理含义上与NUV-r是类似的,都可以反映恒星形成活动。在分析中发现,fHI与NUV-r之间的相关比fH2与NUV-r之间的相关更强；而fH2与W3-W2之间的相关比fHI与NUV-r之间的相关更强。该结果表明W3-W2能比较好地示踪恒星形成星系的分子气体比例fH2。3).我们还发现分子气体质量MH2与12μm红外光度L12μm之间有一个紧致的线性相关。该结果的重要性在于,可以利用L12μm来估算恒星形成星系的MH2,从而为目前稀缺的大样本MH2提供足够多的数据。 除了对近邻正常星系中一般的分子气体成分进行观测研究,我们还利用IRAM30米望远镜对一批活动星系(有星暴和/或AGN活动)进行了致密分子气体谱线(HCN,HCO+(1-0),C2H)以及它们的同位素分子的观测。该观测首次在一个活动星系样本中得到了C2H的系统探测,并首次在这些星系中探测到一些稀有分子谱线(H13CN,HC15N andH13CO+)。我们的估算表明HCN在这些星系中有着中等的光学厚度(丁～1—5)。另外我们使用多分子谱线强度比的诊断方法(HCN/HCO+,C2H/HCN,and C2H/HCO+)讨论了与红外光度的关系。仅在高红外光度的几个复合型活动星系(AGN+SB)中,谱线强度比呈现出与红外光度的微弱相关：HCN/HCO+随着红外光度LIR升高而上升,但C2H/HCN与C2H/HCO+随着LIR升高而下降。我们倾向于认为,不同星系中平均气体密度的不同很可能是影响这些谱线性质的主要因素。 我在攻读博士学位阶段,通过这几项针对不同空间尺度上分子气体的观测研究,得到了射电亚毫米波天文观测研究的全面锻炼,得到了一些有意义的创新科学结果,增进了对分子云与恒星形成之间关系的认识,也积累了许多重要的-手观测数据,为下一步结合流行的化学模型,和物理分析方法进行深入的研究奠定了厚实的基础。
[Abstract]:Hydrogen atoms and molecule cold gases exist widely in interstellar space (ISM) and are the most direct raw materials for star formation and galaxy evolution. By observing and studying the cold gases in galaxies, we can explore and understand the radiation mechanism of Astrophysics and the chemical processes in celestial bodies. Advances in millimeter-wave telescopes have enabled the detection and comparison of molecular spectra at different scales from a large number of molecules with different transitions, the discovery of phenomena associated with star formation and galaxy evolution, the construction of relevant physical interpretations and chemical network models, which have led to the formation of stars in the Milky Way. Under this background, in order to better understand the properties of molecular gases at different scales and the physical phenomena associated with star formation, several frontier observations and studies have been carried out. These works are aimed at the large span of space scale. The scientific objectives also overlap.
We first observed high-resolution submillimeter-wave interferometer (SMA) measurements in some massive star-forming regions of the Milky Way (AFGL490, ON1, W33Main, G10.6-0.4, about 0.1 pc) and studied the 3-2 transitions of typical carbon chain molecules C2H. It was found that C2H was associated with a dense molecular cladding on a larger scale, but the radiation peaks of C2H were generally associated with the dense molecular cladding. The radial abundance distribution is related to the distance from the hot nucleus in the star forming region. It is low in the center of the hot nucleus and high in the corresponding molecular cladding in some regions. The results are in agreement with the prediction of the chemical properties of C2H by the chemical model, but higher in the sky. Inter-resolution data can help to test the model at a smaller scale. This work not only accumulates important information for further understanding of molecular gases and star formation by astrochemical methods, but also provides a good reference for us to extend this understanding to neighboring galaxies.
The focus of our study is on the formation of galaxies in nearby stars, and CO2-1 spectra of a number of gas-rich galaxies have been observed using the submillimeter wave telescope (SMT) with a corresponding scale of about 1-10 kpc. Our Galaxy sample is characterized by the fact that the mass of the star in the target source is moderately low (M*-108.5 M-1010.2 M &, and the parent sample is ALFALF. A neutral hydrogen catalogue is obtained by crossing WISE infrared satellite catalogue. The similarities and differences between the samples and AMIGA and COLDGASS are analyzed and compared. The relationship between the molecular gas mass (MH2) and the neutral hydrogen mass (MHI) of galaxies and other physical parameters (star mass, NUV-r color and infrared color W3-W2) is discussed. The results show that (1) in low-and medium-mass galaxies (M * < 1010M &), MHI / M * increases with the decrease of galaxy mass, but MH2 / M * is almost unchanged; 2) We introduce a new infrared parameter W3-W2, which is similar to NUV-r in physical meaning and can reflect the activity of star formation. The correlation between fH2 and W3-W2 is stronger than that between fHI and NUV-r. The results show that W3-W2 can better trace the molecule-gas ratio fH2.3 of star-forming galaxies. We also find that there is a close linear correlation between the molecular gas mass MH2 and the infrared luminosity L12 micron. The point is that the MH2 of star formation galaxies can be estimated at L12 micron, providing enough data for the current scarce large sample MH2.
In addition to observing the general molecular gas composition in nearby normal galaxies, we have also observed dense molecular gas lines (HCN, HCO+ (1-0), C2H) and their isotope molecules in a number of active galaxies (with starbursts and/or AGN activity) using the IRAM 30-meter telescope. This observation is the first time in an active galaxy sample. We have detected some rare molecular lines (H13CN, HC15N and H13CO+) in these galaxies for the first time. Our estimates show that HCN has a moderate optical thickness (D-1-5) in these galaxies. In addition, we have discussed infrared spectra using the diagnostic method of multi-molecular line intensity ratio (HCN/HCO+, C2H/HCN, and C2H/HCO+). In only a few complex active galaxies (AGN + SB) with high infrared luminosity, the spectral line intensity ratio shows a weak correlation with infrared luminosity: HCN / HCO + increases with the increase of infrared luminosity LIR, but C2H / HCN and C2H / HCO + decrease with the increase of LIR. We tend to think that the average gas density varies very well in different galaxies. It can be a major factor affecting the properties of these spectral lines.
During my Ph.D. program, through these observations of molecular gases at different spatial scales, I obtained a comprehensive exercise in radio submillimeter-wave astronomical observations, obtained some meaningful and innovative scientific results, enhanced the understanding of the relationship between molecular clouds and star formation, and accumulated many important hands. The observation data lay a solid foundation for further study on the combination of popular chemical models and physical analysis methods.
【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：P148
本文编号：2184134
[Abstract]:Hydrogen atoms and molecule cold gases exist widely in interstellar space (ISM) and are the most direct raw materials for star formation and galaxy evolution. By observing and studying the cold gases in galaxies, we can explore and understand the radiation mechanism of Astrophysics and the chemical processes in celestial bodies. Advances in millimeter-wave telescopes have enabled the detection and comparison of molecular spectra at different scales from a large number of molecules with different transitions, the discovery of phenomena associated with star formation and galaxy evolution, the construction of relevant physical interpretations and chemical network models, which have led to the formation of stars in the Milky Way. Under this background, in order to better understand the properties of molecular gases at different scales and the physical phenomena associated with star formation, several frontier observations and studies have been carried out. These works are aimed at the large span of space scale. The scientific objectives also overlap.
We first observed high-resolution submillimeter-wave interferometer (SMA) measurements in some massive star-forming regions of the Milky Way (AFGL490, ON1, W33Main, G10.6-0.4, about 0.1 pc) and studied the 3-2 transitions of typical carbon chain molecules C2H. It was found that C2H was associated with a dense molecular cladding on a larger scale, but the radiation peaks of C2H were generally associated with the dense molecular cladding. The radial abundance distribution is related to the distance from the hot nucleus in the star forming region. It is low in the center of the hot nucleus and high in the corresponding molecular cladding in some regions. The results are in agreement with the prediction of the chemical properties of C2H by the chemical model, but higher in the sky. Inter-resolution data can help to test the model at a smaller scale. This work not only accumulates important information for further understanding of molecular gases and star formation by astrochemical methods, but also provides a good reference for us to extend this understanding to neighboring galaxies.
The focus of our study is on the formation of galaxies in nearby stars, and CO2-1 spectra of a number of gas-rich galaxies have been observed using the submillimeter wave telescope (SMT) with a corresponding scale of about 1-10 kpc. Our Galaxy sample is characterized by the fact that the mass of the star in the target source is moderately low (M*-108.5 M-1010.2 M &, and the parent sample is ALFALF. A neutral hydrogen catalogue is obtained by crossing WISE infrared satellite catalogue. The similarities and differences between the samples and AMIGA and COLDGASS are analyzed and compared. The relationship between the molecular gas mass (MH2) and the neutral hydrogen mass (MHI) of galaxies and other physical parameters (star mass, NUV-r color and infrared color W3-W2) is discussed. The results show that (1) in low-and medium-mass galaxies (M * < 1010M &), MHI / M * increases with the decrease of galaxy mass, but MH2 / M * is almost unchanged; 2) We introduce a new infrared parameter W3-W2, which is similar to NUV-r in physical meaning and can reflect the activity of star formation. The correlation between fH2 and W3-W2 is stronger than that between fHI and NUV-r. The results show that W3-W2 can better trace the molecule-gas ratio fH2.3 of star-forming galaxies. We also find that there is a close linear correlation between the molecular gas mass MH2 and the infrared luminosity L12 micron. The point is that the MH2 of star formation galaxies can be estimated at L12 micron, providing enough data for the current scarce large sample MH2.
In addition to observing the general molecular gas composition in nearby normal galaxies, we have also observed dense molecular gas lines (HCN, HCO+ (1-0), C2H) and their isotope molecules in a number of active galaxies (with starbursts and/or AGN activity) using the IRAM 30-meter telescope. This observation is the first time in an active galaxy sample. We have detected some rare molecular lines (H13CN, HC15N and H13CO+) in these galaxies for the first time. Our estimates show that HCN has a moderate optical thickness (D-1-5) in these galaxies. In addition, we have discussed infrared spectra using the diagnostic method of multi-molecular line intensity ratio (HCN/HCO+, C2H/HCN, and C2H/HCO+). In only a few complex active galaxies (AGN + SB) with high infrared luminosity, the spectral line intensity ratio shows a weak correlation with infrared luminosity: HCN / HCO + increases with the increase of infrared luminosity LIR, but C2H / HCN and C2H / HCO + decrease with the increase of LIR. We tend to think that the average gas density varies very well in different galaxies. It can be a major factor affecting the properties of these spectral lines.
During my Ph.D. program, through these observations of molecular gases at different spatial scales, I obtained a comprehensive exercise in radio submillimeter-wave astronomical observations, obtained some meaningful and innovative scientific results, enhanced the understanding of the relationship between molecular clouds and star formation, and accumulated many important hands. The observation data lay a solid foundation for further study on the combination of popular chemical models and physical analysis methods.
【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：P148
【共引文献】
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2 吴忠祖;;射电天文学课程教学方法改革初探[J];长春教育学院学报;2014年14期
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4 宁长春;张辉杰;;大质量恒星形成区中CO分子外向流的观测和研究[J];西藏大学学报(自然科学版);2013年02期
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