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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/7182

    Title: 利用數星方法研究本銀河系結構;Constraining Galactic Structure by Star Count Method
    Authors: 陳炳志;Bing-Chih Chen
    Contributors: 物理研究所
    Keywords: 本銀河系結構;金屬豐度;紅化分佈;BATC巡天觀測;光譜能量分佈;Galactic structure;metal abundance;reddening distribution;BATC sky survey;spectral energy distribution
    Date: 2001-01-03
    Issue Date: 2009-09-22 10:51:41 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 在本論文中,我們應用了傳統的半經驗式 --- 三單元模型來描述本銀河系的結構。利用不同的樣本,包含了球狀星團與太陽附近的星球之光度函數和海斯圖形來代表不同單元的特性,配合紅化的數值分佈地圖,便可以由星族統計的方法預估不同方向,不同視場大小星場內的星等與顏色分佈。藉由比較觀測得到的星數統計,便可以限制本銀河系結構的參數,這些結構參數包含了不同單元的比例、各單元的比例高度與比例長度、盤面的紅化分佈等等。在本文中,我們利用觀測資料探討了盤面紅化分佈與 不同單元比例的兩個問題。 盤面紅化分佈一直是相關研究中相當複雜的一個課題,我們僅用了盤面星場 SA 98 三個波段的短曝光影像,成功的得到了該方向上2 Kpc 內的紅化分佈與盤面的比例長度。這個獨特的想法與嘗試所得到的結果和其他方法得到的相同,這也證明了數星方法在分佈複雜的盤面上仍然可以有效的進行結構分析。在單元比例的研究上,我們利用六個不同銀緯方向星場的顏色數星來嘗試限制厚盤面的比例,在我們的分析中可以得到厚盤面的星數比例為$5.0 pm 0.5\%$,同時由信心水準的分析,厚盤面的存在是必要的,這樣的結果強烈的支持三單元模型的正確性。 在我們的研究中,也檢討了傳統數星模型的缺陷,並且做了一個很大膽的嘗試:將星球演化模型與星球大氣模型的結果結合數星模型應用於本銀河系的結構研究上。這樣的結合可以突破傳統半經驗式的限制,將數星方法擴展至 Johnson 系統以外的其他光度系統, 同時在這個過程中加入了新的結構參數:金屬豐度比例與梯度,藉由不同等時線的混合以避開了單元代表樣本選取的問題。這些改進使得新的理論數星模型可以應用於數個目前正在進行中的數位深度巡天觀測計畫(Digital deep sky survey)的資料上。我們選取北京天文台 BATC 巡天觀測的中銀緯星場 T329 進行數星統計以驗證新的模型預測結果,我們的結果證明了根據球狀星團與疏散星團所推得各單元的金屬豐度比例與梯度結果和數星方法所導出之結果是非常相符的。在這些巡天計畫的數據陸續發表後,我們可以藉由這個新模型對本銀河系的結構能夠有更清楚的描述。 In my work, I adopted a semi-empirical and 3 components model to describe the structure of Milky way. The luminosity functions and Hess diagrams of the tracers, including globular clusters and solar neighborhood stars, were selected to represent the global properties of their corresponding components. By using the reddening map constructed by other survey, magnitude and color counts can be evaluated through the model by giving the direction and the size of field of view. The structure parameters, for example, the scale length and height of the components, radial distribution of the reddening in disk and the fraction of the components, can be constrained by fitting the observed starcounts. The radial distribution of the reddening in the Galactic disk and fraction of the thick disk component were explored by snap images. The strong absorption and reddening in the Galactic disk is a complicated issue in either optical or infrared astronomy. 3 short exposed BVI images of SA 98 were obtained in order to study the radial distribution along the line of sight. A non-exponential form of the reddening within 2 Kpc was confirmed as well as we also constrained the scale length of the disk by the giant stars. Our result shows the scale length of the disk is around 2.0 Kpc, almost the low limit of other studies. Another 6 fields were analyzed for derive the fraction of the thick disk. a $5.0 pm 0.5$\% thick disk is necessary to agree with the observation data under strong confidence level. Our conclusion mighty support the existence of the disputable component thick disk. We also reviewed the defects of the traditional starcount model and make some attempts to improve the model. An essential effort is to bring the stellar atmosphere and evolution models into the starcount models. Such development can break the restrictions of the old model and extend the starcount method to the bandpasses other than traditional Johnson photometry system. Upon this pure theoretical model was constructed, new parameters of the metal abundance fractions and gradient were introduced to prevent the bias coming from the selection of component tracers in conventional model. This new model is suitable for the applications of some going-on modern deep sky surveys. A intermediate Galactic latitude field T329 were provided by BATC survey which is carried out by Beijing astronomical Observatory to verify the new starcount model. The excellent agreements suggest the new model is work and the metal abundance distribution derived from globular as well as open clusters consists with the result derived from starcounts. We can have more detail descriptions on the Galactic structure by this new model after the catalog of the modern sky surveys are published in the soon future.
    Appears in Collections:[物理研究所] 博碩士論文

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