【摘要】：氫的原子與分子冷氣體廣泛存在于恒星際空間(ISM),是恒星形成活動(dòng)和星系演化過程中最直接的原料,通過對(duì)星系中冷氣體觀測(cè)研究,可以探索和理解天體物理的輻射機(jī)制,以及天體中的化學(xué)過程。近年來得益于觀測(cè)設(shè)備,尤其是射電亞毫米波望遠(yuǎn)鏡的技術(shù)進(jìn)步,在不同尺度上,大量來自于不同分子、不同躍遷的分子譜線得以被探測(cè)和比較,伴隨著恒星形成與星系演化的各種現(xiàn)象被發(fā)現(xiàn),相關(guān)的物理解釋方法、化學(xué)網(wǎng)絡(luò)模型得以被構(gòu)建,這使得人們對(duì)銀河系中恒星形成、對(duì)星系演化的物理圖景的理解得到了前所未有的更新。本論文是在這個(gè)背景下,為了更好地理解不同尺度上分子氣體的性質(zhì),以及與恒星形成相關(guān)的物理現(xiàn)象,開展了幾項(xiàng)前沿觀測(cè)研究工作。這幾項(xiàng)工作針對(duì)的空間尺度跨度很大,具體的科學(xué)目標(biāo)也互有交叉： 我們首先對(duì)銀河系的一些大質(zhì)量恒星形成區(qū)(AFGL490、ON1、W33Main、G10.6-0.4,尺度約為0.1pc)進(jìn)行了亞毫米波干涉儀(SMA)的高分辨率觀測(cè),研究了典型的碳鏈分子C2H的3-2躍遷,發(fā)現(xiàn)在較大尺度上C2H與致密的分子包層成協(xié),但C2H的輻射峰值普遍與恒星形成區(qū)中心有偏移(約幾萬AU的尺度),而它的徑向豐度分布與距離恒星形成區(qū)熱核的距離有關(guān),它在熱核中心豐度較低,而在一些區(qū)域?qū)?yīng)的分子包層中豐度較高。該工作結(jié)果與化學(xué)模型對(duì)C2H的化學(xué)性質(zhì)的預(yù)測(cè)是符合的,而更高空間分辨率的數(shù)據(jù)可以幫助在更小尺度上對(duì)模型進(jìn)行檢驗(yàn)。這項(xiàng)工作既為將來進(jìn)一步通過天體化學(xué)方法去理解分子氣體與恒星形成,積累了重要的信息,也為我們把這種理解拓展到近鄰星系提供了良好的參考。 我們研究的重點(diǎn)集中在近鄰的恒星形成星系,使用亞毫米波望遠(yuǎn)鏡(SMT)對(duì)一批富氣體星系進(jìn)行了CO2-1譜線觀測(cè)(對(duì)應(yīng)尺度約為1-10kpc)。我們的星系樣本的特點(diǎn)在于目標(biāo)源的恒星質(zhì)量是中等偏低的(M*～108.5M& -1010.2M& ),并且母樣本是由ALFALFA中性氫星表與WISE紅外衛(wèi)星星表交叉而得。我們結(jié)合多波段數(shù)據(jù),分析比較了樣本與AMIGA、COLDGASS巡天的異同,討論了星系的分子氣體質(zhì)量(MH2)以及中性氫氣體質(zhì)量(MHI)與星系其他物理參數(shù)(恒星質(zhì)量,NUV-r顏色以及紅外顏色W3-W2等)的關(guān)系。結(jié)果顯示1).在中低質(zhì)量星系(M*≤1010M& )中,MHI/M*明顯隨著星系質(zhì)量減小而升高,但MH2/M*幾乎不變；2).我們引入了一個(gè)新的紅外參數(shù)W3-W2,它在物理含義上與NUV-r是類似的,都可以反映恒星形成活動(dòng)。在分析中發(fā)現(xiàn),fHI與NUV-r之間的相關(guān)比fH2與NUV-r之間的相關(guān)更強(qiáng)；而fH2與W3-W2之間的相關(guān)比fHI與NUV-r之間的相關(guān)更強(qiáng)。該結(jié)果表明W3-W2能比較好地示蹤恒星形成星系的分子氣體比例fH2。3).我們還發(fā)現(xiàn)分子氣體質(zhì)量MH2與12μm紅外光度L12μm之間有一個(gè)緊致的線性相關(guān)。該結(jié)果的重要性在于,可以利用L12μm來估算恒星形成星系的MH2,從而為目前稀缺的大樣本MH2提供足夠多的數(shù)據(jù)。 除了對(duì)近鄰正常星系中一般的分子氣體成分進(jìn)行觀測(cè)研究,我們還利用IRAM30米望遠(yuǎn)鏡對(duì)一批活動(dòng)星系(有星暴和/或AGN活動(dòng))進(jìn)行了致密分子氣體譜線(HCN,HCO+(1-0),C2H)以及它們的同位素分子的觀測(cè)。該觀測(cè)首次在一個(gè)活動(dòng)星系樣本中得到了C2H的系統(tǒng)探測(cè),并首次在這些星系中探測(cè)到一些稀有分子譜線(H13CN,HC15N andH13CO+)。我們的估算表明HCN在這些星系中有著中等的光學(xué)厚度(丁～1—5)。另外我們使用多分子譜線強(qiáng)度比的診斷方法(HCN/HCO+,C2H/HCN,and C2H/HCO+)討論了與紅外光度的關(guān)系。僅在高紅外光度的幾個(gè)復(fù)合型活動(dòng)星系(AGN+SB)中,譜線強(qiáng)度比呈現(xiàn)出與紅外光度的微弱相關(guān)：HCN/HCO+隨著紅外光度LIR升高而上升,但C2H/HCN與C2H/HCO+隨著LIR升高而下降。我們傾向于認(rèn)為,不同星系中平均氣體密度的不同很可能是影響這些譜線性質(zhì)的主要因素。 我在攻讀博士學(xué)位階段,通過這幾項(xiàng)針對(duì)不同空間尺度上分子氣體的觀測(cè)研究,得到了射電亞毫米波天文觀測(cè)研究的全面鍛煉,得到了一些有意義的創(chuàng)新科學(xué)結(jié)果,增進(jìn)了對(duì)分子云與恒星形成之間關(guān)系的認(rèn)識(shí),也積累了許多重要的-手觀測(cè)數(shù)據(jù),為下一步結(jié)合流行的化學(xué)模型,和物理分析方法進(jìn)行深入的研究奠定了厚實(shí)的基礎(chǔ)。
[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.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：P148

【共引文獻(xiàn)】

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本文編號(hào)：2184134