本文選題：星際介質 + 分子云�。� 參考：《南京大學》2016年博士論文

【摘要】：大質量恒星,通常指8倍太陽質量以上的恒星,在天體物理各領域的研究中都有重要的影響。它們主導了星團的光度,其強烈的星風、紫外波段的發(fā)射、死亡時的超新星爆發(fā)劇烈地影響星際介質的構成和能量平衡,所以研究其如何形成具有重要的意義。對于大質量恒星形成,近十年的觀測和理論研究取得了很多進展,例如我們已經明確,大質量恒星誕生于分子云中的大質量稠密核內,并且傾向于成團形成。然而,若干有關大質量稠密核的重要問題仍然沒有得到解決。例如:大質量稠密核是否普遍處在位力平衡狀態(tài);湍動和磁場對稠密核的形成和演化有何作用;星系中心附近的極端物理環(huán)境下稠密核的形成是否受到影響。因此,本文根據對銀河系內若干大質量恒星形成區(qū)的亞毫米波和射電波段的高空間分辨率觀測,討論了三個問題:1)大質量恒星形成區(qū)中稠密核的統(tǒng)計性質;2)處在早期演化階段的大質量團塊的碎裂過程和稠密核的動力學狀態(tài);3)銀河系中心附近分子云中的大質量稠密核性質。這三個問題從不同角度探討了大質量稠密核的形成和塌縮過程,對于理解大質量恒星的形成有重要意義。與上述三個問題對應,我們具體介紹了三項觀測研究:·對62個大質量恒星形成區(qū)的甚大陣氨分子譜線巡測,以得到稠密核的溫度、線寬、質量、位力參數等統(tǒng)計性質;·對紅外暗云G28.53-0.25的(增容)甚大陣氨分子譜線和脈澤、綠堤射電望遠鏡氨分子譜線以及亞毫米波射電望遠鏡陣塵埃連續(xù)譜和分子譜線的綜合觀測,以研究團塊的碎裂和稠密核的動力學狀態(tài)以及恒星形成活動;·對中央分子帶中6塊巨分子云的央斯基甚大陣氨分子譜線、水脈澤和射電連續(xù)譜,以及亞毫米波射電望遠鏡陣連續(xù)譜和分子譜線的觀測,以研究其中的稠密氣體分布和恒星形成活動。我們發(fā)現(xiàn),在約1 pc尺度的團塊或纖維進一步碎裂過程中,只考慮熱運動的支撐作用得到的碎裂產物質量一般只有幾個M(?),遠小于觀測到的稠密核質量,而考慮湍動的支撐作用后,碎裂的結果與稠密核質量一致,使得大質量稠密核的形成成為可能。另一方面,中央分子帶中缺乏內部致密結構的幾個分子云似乎暗示極強的湍動也會阻止碎裂過程和后續(xù)稠密核的形成,導致恒星形成活動不活躍。這表明大質量稠密核的形成過程中湍動起到重要作用。另外我們發(fā)現(xiàn),在只考慮湍動和熱運動支撐作用的情況下,稠密核的位力參數普遍小于臨界值,表明它們是自引力束縛的。其中較大質量的稠密核的位力參數普遍遠小于1,表明它們嚴重偏離位力平衡狀態(tài)�？紤]到這些稠密核不可能是暫現(xiàn)式的結構,我們需要額外的支撐作用使其更接近位力平衡,一個可能的機制是磁場的支撐。這表明磁場和湍動在控制大質量稠密核的動力學狀態(tài)中可能是同等重要的。
[Abstract]:Large-mass stars, usually those above 8 times the mass of the sun, play an important role in all fields of astrophysics.They dominate the luminosity of star clusters, their strong star winds, ultraviolet emission, and supernova bursts at the time of death have a dramatic impact on the composition and energy balance of interstellar media, so it is of great significance to study how to form them.For the formation of massive stars, much progress has been made in the observation and theoretical studies in the past decade. For example, we have made it clear that large mass stars are born in dense nuclei in the molecular cloud and tend to form clusters.However, some important problems concerning mass dense nuclei are still unsolved.For example, whether large mass dense nuclei are generally in the state of potential force equilibrium, what are the effects of turbulence and magnetic field on the formation and evolution of dense nuclei, and whether the formation of dense nuclei is affected in the extreme physical environment near the center of galaxies.Therefore, based on the high spatial resolution observations of submillimeter waves and radio bands in several massive star forming regions of the Milky way Milky way,In this paper, we discuss three problems: 1) Statistical properties of dense nuclei in the mass star formation region (2) fragmentation of mass masses in the early stage of evolution and 3) large mass dense nuclei in molecular clouds near the center of the Milky way Galaxy.These three problems discuss the formation and collapse process of dense nuclei with large mass from different angles, which is of great significance for understanding the formation of massive stars.Corresponding to the above three problems, we have introduced three observational studies in detail: the very large ammonia molecular spectral line survey in 62 large mass star forming regions is used to obtain the temperature, linewidth, mass of dense nuclei.Statistical properties such as potential force parameters, comprehensive observation of (capacitive) very large ammonia molecular spectra and maser lines of infrared dark clouds G28.53-0.25, ammonia molecular spectra lines of the Green Dike Radio Telescope and dust continuous spectrum and molecular spectral lines of the submillimeter wave radio telescope array,In order to study the dynamic state of fragmentation and dense nuclei and the activity of star formation in the lumps, the Yansky very large array of ammonia molecular lines, water maser and radio continuous spectra of 6 giant molecular clouds in the central molecular band are studied.The continuous spectra and molecular spectral lines of the submillimeter wave radio telescope array are also observed to study the dense gas distribution and star formation activities.It is found that in the further fragmentation of a mass or fiber on the scale of about 1 PC, the mass of the broken product obtained by considering only the support of thermal motion is generally only a few Mucks, which is much smaller than the observed mass of dense nuclei.Considering the support of turbulence, the result of fragmentation is consistent with the mass of dense nucleus, which makes the formation of large mass and dense nucleus possible.On the other hand, several molecular clouds lacking internal dense structures in the central molecular band seem to imply that extremely strong turbulence may also prevent the fragmentation process and the subsequent formation of dense nuclei, resulting in the inactivity of star formation.This indicates that turbulence plays an important role in the formation of large mass dense nuclei.In addition, we find that the potential force parameters of dense nuclei are generally smaller than the critical values, which indicates that they are bound by self-gravity.The potential force parameters of the dense nuclei with larger mass are generally much less than 1, indicating that they deviate seriously from the potential force equilibrium state.Considering that these dense nuclei cannot be temporary structures, we need additional support to make them closer to the potential force balance. One possible mechanism is magnetic field support.This suggests that the magnetic field and turbulence may be equally important in controlling the dynamic state of dense nuclei with large mass.
【學位授予單位】：南京大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：P152;P161
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本文編號：1739975