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研究生： 王靖華
Jing-hua Wang
論文名稱： 年輕疏散星團NGC884和NGC663之恆星計數
Star counts in open cluster NGC884 and NGC663
指導教授： 傅學海
Fu, Hsieh-Hai
學位類別： 碩士
Master
系所名稱： 地球科學系
Department of Earth Sciences
論文出版年： 2000
畢業學年度： 88
語文別： 英文
論文頁數： 37
中文關鍵詞： 疏散星團 、恆星計數
英文關鍵詞： open cluster, star counts, king model
論文種類： 學術論文
相關次數： 點閱：225  下載：13 
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    • 疏散星團集中於銀河盤面附近，屬於年輕的恆星系統。對疏散星團的研究有助於了解恆星的形成與銀河結構與演化。本研究以恆星計數的方法，分析疏散星團的恆星個數密度分布，並與金氏模式（King, 1962）擬合，期望由模式中的潮汐半徑（rt） 獲得星團質量的訊息。
    選定的年輕疏散星團為NGC 884 (11.5~14 Myr).和NGC 663 (9~14 Myr)。影像取自帕羅瑪全天巡測的數位化影像（Digitized Palomar Observatory Sky Survey，簡稱DSS）。以下是在假設星團NGC884和NGC 663的距離分別為2500 pc與 2800 pc的結果，因此所選定的1平方度的視野分別相當於43.6 pc ’ 43.6 pc和48.9 pc ’ 48.9 pc。在這樣的視野下，就星團NGC884而言，比completeness instrumental magnitude limit亮的星總共有15381顆星，而在NGC 663中有22353顆星被分析。
    藉由最小方差法與金氏模式擬合，發現NGC884與NGC 663符合金氏模式。其中NGC 884 的最佳參數值分別為k = 23.45 stars/pc2、rc = 3.27 pc 和 rt = 20.72 pc，質量約為3300M⊙。而NGC 663的三個參數值 k = 18.09 stars/pc2、 rc = 4.07 pc和rt = 14.25 pc，質量約1100 M⊙.

    A study of star counts in young open clusters NGC 884 (11.5~14 Myr) and NGC 663 (9~14 Myr) is presented on the basis of images from Digitized Sky Survey (DSS). Within a sky area of 1°*1° centered at the two clusters, there are 15381 stars and 22353 stars brighter than completeness instrumental magnitude limit for NGC884 and NGC663, respectively. The following results are derived from the assumed distance 2500 pc for NGC884 and 2800 pc for NGC 663. From the least square fits to the data, the projected stellar number density distributions is consistent with King's model. The best-fitted parameters for NGC 884 are k = 23.45 stars/pc2, rc = 3.27 pc, and rt = 20.72 pc. Based on the tidal radius, the mass of NGC884 is about 3300 M⊙. For NGC 663, the best-fitted parameters are k = 18.09 stars/pc2, rc = 4.07 pc, and rt = 14.25 pc, with mass ~1100 M⊙.

    Content 1. Introduction...........1 2. Properties of open clusters...........2 3. Image selection 3.1 Review of Palomar sky surveys........3 3.2 Selection of open clusters.........5 4. Image process 4.1 Image processing......11 4.2 Magnitude calibration..............11 4.3 The completeness magnitude limit..............12 4.4 The position of the cluster center.............12 4.5 The projected stellar density distribution...............13 5. Results and Discussion 5.1 NGC 884.............15 5.2 NGC 663............24 5.3 NGC 6709...............33 6. Conclusion..................36 Reference.................37 Appendix A King Model......................i Appendix B Open cluster NGC 7789.....................viii

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