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題名 | Shapley超星系團中星系團的排列=Alignment of Galaxy Clusters in the Shapley Supercluster |
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作者 | 何佩勵; 陳林文; 顏吉鴻; Ho, Pei-li; Chen, Lin-wen; Yan, Chi-hung; Leon,Stephane; Guibert,Jean; |
期刊 | 臺北天文館學報 |
出版日期 | 20041200 |
卷期 | 2 民93.12 |
頁次 | 頁1-9 |
分類號 | 323.84 |
語文 | chi |
關鍵詞 | Shapley超星系團; 星系密集區; 星系團排列; Supercluster; Galaxy overdensity region; Alignment of galaxy clusters; |
中文摘要 | 我們利用Shapley超星系團 (supercluster) 核心A3558附近大約20°×20°天空的星系資料,偵測到220個星系密集區(overdensity region),將其中同屬一個星系團/群內的次結構 (substructure)者合併計算後,我們共得到164個單獨的星系團或星系群,其中有37個包含一個以上的星系密集區在內,可視為正在進行星系團/群合併的候選者 (merger candidate )。利用FLASH的星系紅移資料估算這些星系團/群的紅移速度,並計算其橢圓度及長軸方位角,結果顯示在Shapley超星系團之中,最鄰近的星系團/群之間存在互相排列(alignment)的現象,其中正在進行星系團/群合併的候選者有較為明顯的排列情形。另外,視橢圓度(apparent ellipticity)與最鄰近星系團間的排列角度呈現負相關的趨勢,也就是,橢圓度愈大的星系團/群表現出愈明顯的排列。從我們的結果來看,對於有次結構、較大橢圓度的星系團/群,有較好的排列,這結果與星系團沿著大尺度絲狀結構(large-scale filament structure)非均向性地聚集合併的模式是一致的。至於對超星系團核心A3558的排列,較好的排列侷限於核心附近的Abell星系團,我們尚無法由目前的結果推測Shapley超星系團塌縮(collapse)的範圍。 |
英文摘要 | Using a sample of ~104 galaxies in a 20°×20° sky centered on the core of the Shapley Supercluster, we identify 164 galaxy clusters/groups out of 220 detected galaxy overdensity regions in this area, including 103 previously unknown galaxy systems and 37 cluster merger candidates which consist of more than one overdensity region. Cross-checking with the FLASH redshift survey catalogue, we have further estimated the redshifts of these sources, followed by a series of statistical analysis to study the formation history of the supercluster. The clusters/groups in the Shapley Supercluster show a tendency of alignment with their nearest neighbors, and the alignment signal is stronger for the merger candidates. In addition, we note that clusters/groups with larger ellipticity are better aligned with their nearest clusters, which suggests the apparent ellipticities of clusters and their alignment angles are anti-correlated. Both results indicate that the Shapley Supercluster was formed in accordance with the anisotropic accreting scenario of galaxy clusters formation along the large scale filaments. The signal of cluster alignment with the core of the Shapley Supercluster (A3558) is however weak, only marginally detected in a few Abell clusters in the vicinity of core, thus more galaxy velocity data are required to further constrain the collapse region of the Shapley Supercluster. |
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