探討薛普利超星系團中環境對星系活動的影響

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(1)國立臺灣師範大學地球科學系博士論文 Department of Earth Sciences National Taiwan Normal University Doctoral Dissertation. 探討薛普利超星系團中環境對星系活動的影響 Environmental Effects on Galaxy Activities in the Shapley Supercluster 何佩勵 Ho, Pei-Li. 指導教授：陳林文教授 (Prof. Chen, Lin-Wen). 中華民國 102 年 7 月.

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(3) 摘要在這篇研究中，我們利用許多不同波段的巡天資料和從 NASA 河外資料庫(NED) 收集的星系紅移資料，來探討在薛普利超星系團中，星系的恆星形成及星系核心的活動是如何受到來自星系團合併、星系團質量、星系團內介質(ICM)及星系密度等環境因素和星系本身恆星質量的影響。這些巡天資料目錄包括 2 微米巡天(2MASS)，6 度視野星系巡天(6dFGS)，國家電波天文台甚大天線陣巡天 (NVSS)，倫琴衛星巡天(RASS)和倫琴衛星-歐南天文台 X 射線星系團目錄 (REFLEX)。藉著利用星系光譜的 4000Å 轉折強度(4000Å break strength，D4000)做為星系恆星形成歷史的指標，並代表星系中恆星的平均年齡。我們在 4000Å 轉折強度與星系密度的關係中，我們發現星系中恆星的平均年齡與周圍星系的密度以及星系本身的恆星質量大小都有很強的相關性。特別是當星系密度的計算是以 1 Mpc 的尺度為半徑所得到的密度值，其相關性最好。為了探討星系團的環境對於其成員星系在 4000Å 轉折強度和該星系至星系團核心距離的關係(D4000-radius)上的影響，我們將 69 個在薛普利超星系團中的星系團和星系群依其維里質量(virial mass，以 M200 表示)高低、X 射線的強度、以及是否顯示星系團合併的特徵等特性各分成 2 個族群，並且將距離星系團核心 5 倍維里半徑(virial radius,以 r200 表示)內的星系依其在Ｋ波段的絕對星等高低（代表星系的恆星質量）分成 4 個範圍，結果顯示：（1）對所有不同特性的星系團族群，其 4000Å 轉折強度隨星系至星系團核心距離的變化，都與成員星系的恆星質量有關。（2）對分別在 4 個星系恆星質量範圍的星系來說，在較高質量及Ｘ射線強度的星系團中的星系，其平均星系年齡都比在較低質量、X 射線的星系團中的星系老。（3）對於位於合併中的星系團 5 倍維里半徑內的低質量星系，其平均年齡都較在非合併中的星系團中的低質量星系年輕。（4）對依星系團特性而區分的 2 個星系團族群來說，兩者間的差異以低質量星系最明顯，這表示低質量、氣體豐度高的星系對環境的影響最敏感。另外，我們也利用由電波源所辨識的恆星形成星系(star-forming galaxy， SFG)及吸收線活躍星系核(absorption-line AGN，AA)來了解環境對星系活動的影響。結果顯示，星系中恆星形成星系的比率隨著環境星系密度的增加而快速降低；反之，吸收線活躍星系核的比率隨著星系密度的增加而增加。另外，我們也發現，在合併中且其速度瀰散度(velocity dispersion)大於 500 公里/秒的星系團外圍，距離星系團核心 1-2 倍半徑的地方，恆星形成星系的比率特別高。這可能是因為當星系從絲狀結構落入星系團的時候，因星系密度增加且星系彼此間的相對速度低，使得星系間因互相作用而觸發恆星的形成。最後，我們利用 Abell S0721 這個在薛普利超星系團中，擁有最高比率吸收線活躍星系核、並且是正在合併中的星系團，來研究其動力狀態與成員星系活動的關係。由於吸收線活躍星系核的電波發射來源被認為與星系本身或周圍的星系團熱氣體之熱動力狀態有關，我們因此推測，在這個星系團中，吸收線活躍星系核所在的次結構應該是在較穩定的狀態。因此我們可以利用運動方程式的解(equations of motion)來推測目前 S0721 可能的合併狀態。關鍵字:超星系團、4000Å 轉折強度、恆星形成、星系團合併.

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(5) Environmental Effects on Galaxy Activities in the Shapley Supercluster. Pei-Li Ho. Department of Earth Sciences National Taiwan Normal University July 2013.

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(7) ABSTRACT We use several survey catalogues in different wavelengths, including the Two Micro All Sky Survey (2MASS), Six-degree Field Galaxy Survey (6dFGS), NRAO VLA Sky Survey (NVSS), ROSAT All Sky Survey (RASS), ROSAT-ESO Flux Limited X-ray (REFLEX) cluster catalogue, and galaxy velocity data from the the NASA Extragalactic Database (NED), to study how galaxy star formation and nuclear activity depend on the environmental effects from cluster/group mergers, halo mass, the intracluster medium (ICM) and local galaxy density as well as on galaxy stellar mass (indicated by the K-band absolute magnitude Mk ) in the Shapley supercluster (SSC). By using the 4000 Å break strength (D4000) as an indicator of star formation history, the relation between the D4000 and local galaxy density (D4000–density) shows that the D4000 is strongly dependent on the local galaxy density as well as the on galaxy stellar mass. The D4000–density correlation is strongest for density estimated on scale of 1 Mpc for all Mk ranges. As to the cluster/group environmental effects on the relations of D4000 and clustercentric distance (D4000–radius) for galaxies within 5 r200 , it is analyzed by dividing the 69 clusters/groups in the SSC into two populations based on the difference in M200 , X-ray flux, and merger features, respectively, as well as by dividing the selected galaxies into 4 subclasses based on their Mk . Our results show that: (1) The D4000–radius relation depend strongly on galaxy stellar mass for all cluster/group populations. (2) For more massive, Xray detected clusters, the mean strength of 4000 Å break is mostly stronger than the less massive, under X-ray detection ones, even out to 3–5 r200 for all Mk ranges. (3) In merging clusters, the faint low-mass galaxies are younger (lower D4000) than those in non-merging systems from cluster center out to 3–5 r200 , and the enhanced star formation activity is possibly triggered by merging events. (4) The difference in the D4000–radius relations between the two divided populations shown in this study is most pronounced for low-mass galaxies, this means that low-mass, gas-rich galaxies are most sensitive to their environments. The environmental effects on galaxy activities are also analyzed by the fractions of radio-selected star-forming galaxies (SFG) and absorption-line AGN (AA). Our results show that the fraction of SFG drops quickly towards high galaxy density regions, whereas the fraction of AA increases towards denser regions. The cluster/group environmental effects on the fSFG –radius relation show that there is an obvious enhanced fraction within 1–2 r200 . A possible scenario for this enhancement may be owing to the increasing galaxygalaxy interactions when galaxies are infalling into clusters. The outskirt regions for this enhancement are mostly related to on-going cluster mergers with σv ≥ 500 km s−1 . Finally, we investigate the possible connection between cluster dynamical state and the properties of its member galaxies for one cluster merger Abell S0721. In this cluster, it shows strong evidence of three substructures, and owns the highest fraction of radio-emitting galaxies among the clusters in the SSC. A total of three AA and two SFG are identified. For each AA, it is also the brightest galaxy in each substructure core. Assuming the gas supply of AA is frequently associated with the thermodynamic states of galactic coronae or host groups and clusters, therefore, the possible scenario from solutions of the equations of motion for this cluster is that the substructure at the north-east is either unbound or is collapsing at a current separation of ∼1.4 Mpc, and the two clumps in the main structure are possibly turning to collapse after the maximum expansion.. Keywords: supercluster, 4000Å break strength, star formation, cluster merger.

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(9) Contents Table of Contents. v. List of Figures. ix. 1. 1 1 2 3 4 4 5. 2. 3. Introduction 1.1 Effects of Cluster Mergers on Member Galaxies . . . . 1.2 Cluster Environmental Effects on Galaxy Activities . . 1.3 Galaxy Star Formation Activity in Outskirts of Clusters 1.4 The Motivation of This Thesis . . . . . . . . . . . . . 1.5 The Shapley Supercluster . . . . . . . . . . . . . . . . 1.6 Outline of This Thesis . . . . . . . . . . . . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. . . . . . .. Data 2.1 Data Catalogues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.1 Two Micro All Sky Survey . . . . . . . . . . . . . . . . . . . . . . 2.1.2 Six-degree Field Galaxy Survey . . . . . . . . . . . . . . . . . . . 2.1.3 NRAO VLA Sky Survey . . . . . . . . . . . . . . . . . . . . . . . 2.1.4 ROSAT All Sky Survey and ROSAT-ESO Flux Limited X-ray (REFLEX) Cluster Catalogue . . . . . . . . . . . . . . . . . . . . . . 2.1.5 Velocity data from the NASA Extragalactic Database . . . . . . . . 2.2 Galaxy Velocity Catalogue, Completeness and Galaxy Distribution . . . . . 2.2.1 Velocity catalogue . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.2 Data completeness . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.3 Galaxy distribution . . . . . . . . . . . . . . . . . . . . . . . . . . Properties of Galaxy Clusters and Groups in the SSC 3.1 Compilation and Identification of Galaxy Clusters and Groups . . . . . . . 3.1.1 Galaxy clusters and groups compiled from the NED . . . . . . . . 3.1.2 X-ray detected galaxy clusters and groups . . . . . . . . . . . . . . 3.1.3 Detection of unidentified galaxy groups . . . . . . . . . . . . . . . 3.1.4 Determination of velocity dispersion σv , r200 , M200 , and cluster members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Dynamic States of Galaxy Clusters and Groups . . . . . . . . . . . . . . . 3.2.1 DS-test probability of galaxy clusters and groups . . . . . . . . . . 3.2.2 Ellipticities of galaxy clusters and groups . . . . . . . . . . . . . . 3.3 Summary of Properties of Galaxy Clusters and Groups in the SSC . . . . . 3.4 Alignment of Galaxy Clusters in the SSC . . . . . . . . . . . . . . . . . . 3.4.1 Identification of galaxy clusters/groups and calculation of ellipticities 3.4.2 Alignment of clusters/groups in the SSC . . . . . . . . . . . . . . . v. 7 7 7 8 8 9 10 11 11 11 15 21 21 21 22 22 24 26 26 27 29 37 38 38.

(10) vi. CONTENTS 3.4.3 3.4.4 4. 5. 6. Discussion and conclusion . . . . . . . . . . . . . . . . . . . . . . Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 44 45. Environmental Effects on Galaxy Star Formation History 4.1 Introduction of the 4000 Å Break Strength . . . . . . . . . . . . . . . . . . 4.2 The 4000 Å Break Strength in the SSC . . . . . . . . . . . . . . . . . . . 4.2.1 The relation between D4000 and Mk . . . . . . . . . . . . . . . . . 4.2.2 Spatial distribution of D4000 in the SSC . . . . . . . . . . . . . . . 4.2.3 Relation between D4000 and the local galaxy number density . . . 4.3 Relation of D4000 and Clustercentric Distance . . . . . . . . . . . . . . . 4.3.1 Dependence of D4000 on M200 of host clusters/groups . . . . . . . 4.3.2 Dependence of X-ray detection of host clusters/groups . . . . . . . 4.3.3 Difference of D4000 for clusters/groups with similar M200 or velocity dispersion but different in X-ray detection . . . . . . . . . . . . 4.3.4 Dependence of merging features of host clusters/groups . . . . . . 4.3.5 Summary of the D4000–radius relations . . . . . . . . . . . . . . .. 47 47 49 49 52 52 55 58 63. Environmental Effects on Properties of Radio-Emitting Galaxies 5.1 Identification of Radio-Emitting Galaxy . . . . . . . . . . . . . . . . . . . 5.1.1 Cross-matching of galaxy sample with NVSS . . . . . . . . . . . . 5.1.2 Classification of radio-emitting galaxies . . . . . . . . . . . . . . . 5.1.3 Properties of radio-emitting galaxies . . . . . . . . . . . . . . . . . 5.2 Relations between Galaxy Number Density and Fractions of radio-emitting Galaxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Relations between Local Galaxy Number Density and Properties of Radioemitting Galaxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.1 Dependence of star formation rate, specific star formation rate of SFG on local galaxy number density . . . . . . . . . . . . . . . . . 5.3.2 Dependence of radio luminosity at 1.4 GHz of absorption-line AGN on local galaxy number density . . . . . . . . . . . . . . . . . . . 5.4 Relation of Radio-Emitting Galaxy Fraction and Clustercentric Distance . . 5.4.1 Relation of star-forming galaxy fraction and clustercentric distance 5.4.2 Comparison of the relations of D4000–radius and fSFG –radius . . . 5.4.3 Comparison of the relations of D4000–radius and fSFG –radius for cluster mergers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.4 Relation of absorption-line AGN fraction and clustercentric distance 5.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 64 65 70 75 75 75 76 80 81 87 88 88 89 89 92 96 99 99. A Multi-wavelength Study of the Merger Candidate Abell S0721 and the Activities of Its Member Galaxies 105 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 6.2 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 6.3 Data Analysis and Result . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 6.3.1 Spatial and hardness ratio analysis of X-ray data . . . . . . . . . . 108 6.3.2 Galaxy dynamic and spatial distribution analysis . . . . . . . . . . 109 6.3.3 Identification of radio galaxies in S0721 . . . . . . . . . . . . . . . 111 6.4 Discussioin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 6.4.1 The properties of X-ray emission . . . . . . . . . . . . . . . . . . 114 6.4.2 Mass estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . 117.

(11) vii. CONTENTS. 6.5 7. 6.4.3 Dynamical model . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 6.4.4 Comparison of radio galaxy properties with other mergers in the SSC 120 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123. Summary. 127. Bibliography. 129. A Images of Galaxy Clusters and Groups in the SSC. 137.

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(13) List of Figures 2.1. Velocity distribution of galaxies towards the SSC with 0 ≤ v ≤ 30000 km s−1 12. 2.2. Distribution of K band magnitude for sources from 2MASS XSC and velocity sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.3. 13. Image of projected distribution for fractions of galaxies which have measured velocities in the parent 2MASS catalogue . . . . . . . . . . . . . . .. 14. 2.4. Wedge diagrams in right ascension and declination for galaxies towards SSC. 16. 2.5. Image of projected distribution of galaxy number density for galaxies from the 2MASS catalogue . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.6. Image of projected distribution of fractions for galaxies that belong to the SSC in velocity catalogue . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.7. 17. 18. Images of projected distributions of estimated galaxy number density in the SSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 19. 3.1. Distribution of DS-test probabilities for clusters/groups in the SSC . . . . .. 27. 3.2. Distribution of cluster/group ellipticities in the SSC . . . . . . . . . . . . .. 29. 3.3. Image of projected galaxy density distribution superimposed by cluster/group positions in the SSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3.4. 30. Distribution of cluster redshifts, cluster velocity dispersions, M200 , and r200 in the SSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 31. 3.5. Distributions of apparent ellipticities for different subsamples . . . . . . . .. 39. 3.6. Projected distribution of cluster ellipses with apparent ellipticities . . . . .. 41. 3.7. Alignment angles are shown as a function of distance to A3558 . . . . . . .. 42. ix.

(14) x. LIST OF FIGURES 3.8. Alignment angles to their nearest-neighbor are shown as a function of ellipticities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 43. 4.1. The 6dF spectra for a SFG and a typical early type galaxy . . . . . . . . . .. 48. 4.2. Relation between Mk and D4000 for radio-emission galaxies . . . . . . . .. 50. 4.3. Number of galaxies as a function of D4000 for different ranges of Mk . . .. 51. 4.4. The projected distribution of D4000 in the SSC . . . . . . . . . . . . . . .. 53. 4.5. Wedge diagrams for galaxies with measured D4000 towards the SSC . . . .. 54. 4.6. Relation between mean D4000 and local galaxy number density . . . . . .. 56. 4.7. The D4000–radius and fD4000≤1.4 –radius relations for host clusters with different M200 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 61. 4.8. Related local galaxy density and deviation of D4000 for Figure 4.7 . . . . .. 62. 4.9. The D4000–radius and fD4000≤1.4 –radius relations for host clusters divide by using X-ray detection . . . . . . . . . . . . . . . . . . . . . . . . . . .. 66. 4.10 Related local galaxy density and deviation of D4000 for Figure 4.9 . . . . .. 67. 4.11 Relation of D4000–radius for host groups with similar M200 (velocity dispersion) but with different X-ray detection . . . . . . . . . . . . . . . . . .. 68. 4.12 Related local galaxy density and deviation of D4000 for Figure 4.11 . . . .. 68. 4.13 The D4000–radius and fD4000≤1.4 −radius relations for host clusters with different merger features . . . . . . . . . . . . . . . . . . . . . . . . . . .. 71. 4.14 Related local galaxy density and deviation of D4000 for Figure 4.13 . . . .. 72. 5.1. Distribution of position offsets and probabilities for identification of radioemitting galaxies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 76. 5.2. Examples of four spectral classes from the 6dFGS spectra . . . . . . . . . .. 78. 5.3. Positions of the radio-emitting galaxies are marked on the image of galaxy density distribution in the SSC . . . . . . . . . . . . . . . . . . . . . . . .. 79. 5.4. Histograms of K-band magnitude for different galaxy samples . . . . . . .. 80. 5.5. Histograms of L1.4GHz and Mk for SFG and absorption-line AGN . . . . . .. 82. 5.6. Distribution of star formation rate as a function of Mk . . . . . . . . . . . .. 82. 5.7. Distribution of L1.4HGz as a function of Mk . . . . . . . . . . . . . . . . . .. 83.

(15) xi. LIST OF FIGURES 5.8. Image of projected galaxy number density distribution divide into 5 density ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5.9. 85. The SFG and absorption-line AGN fractions as a function of galaxy number density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 86. 5.10 Histograms of local galaxy number density for SFG, absorption-line AGN and 6dFGS sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 87. 5.11 SFR and SSFR as a function of local galaxy density for 4 Mk ranges . . . .. 89. 5.12 L1.4GHz as a function of local galaxy density for absorption-line AGN with different Mk ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 90. 5.13 Relations of fSFG− radius for host clusters/groups with different properties .. 93. 5.14 Relation of local galaxy density–radius for the 6dFGS and SFG with different host cluster/group properties . . . . . . . . . . . . . . . . . . . . . . .. 94. 5.15 Star formation rate a a function of D4000 . . . . . . . . . . . . . . . . . .. 97. 5.16 Relation of fSFG− radius for host clusters with or without merger features . .. 98. 5.17 Relation of fAA −radius for host clusters/groups with different properties . . 100 6.1. The RASS image of part of the Shapley Supercluster . . . . . . . . . . . . 107. 6.2. Smoothed RASS X-ray images of S0721 . . . . . . . . . . . . . . . . . . . 110. 6.3. The rotated image of the central region of S0721 . . . . . . . . . . . . . . 112. 6.4. Distribution of hardness ratio across the central region of S0721 . . . . . . 113. 6.5. Relation between temperature and countrate hardness ratios . . . . . . . . . 113. 6.6. The radial velocity distribution of S0721 members and the best fit of 3Gaussian model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114. 6.7. The positions of S0721 member galaxies are marked on the ROSAT all sky survey X-ray image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115. 6.8. The smoothed surface number density of S0721member galaxies superposed on the ROSAT all sky survey X-ray image . . . . . . . . . . . . . . 116. 6.9. Relation between measured relative radial velocity (Vr ) and the projection angle θ. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120.

(16) xii. LIST OF FIGURES 6.10 The time interval between the current stage and core-crossing of S0721 as a function of projection angle . . . . . . . . . . . . . . . . . . . . . . . . . . 121 6.11 The distribution of R-band absolute magnitudes and L1.4GHz for radio galaxies in A3558, A3528, A3571 complex, and S0721 . . . . . . . . . . . . . . 124 A.1 Images of distributions of galaxy number density for 69 clusters/groups in the SSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139.

(17) List of Tables 3.1. Properties of X-ray detected clusters in the SSC . . . . . . . . . . . . . . .. 23. 3.2. Properties of galaxy clusters/groups in the SSC . . . . . . . . . . . . . . .. 32. 4.1. Total number of galaxies with different Mk and clustercentric distance ranges for host clusters with M200 larger or less than 2 × 1014 M

(18) . . . . . . . . .. 4.2. Total number of galaxies with different Mk and clustercentric distance ranges for host clusters with or without X-ray detection . . . . . . . . . . . . . . .. 4.3. 77. Total number of SFG and galaxies from the 6dFGS galaxy sample in different clustercentric distance ranges . . . . . . . . . . . . . . . . . . . . . . .. 5.3. 70. Total number of radio-emitting galaxies for each class from velocity sample and those in the SSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5.2. 66. Total number of galaxies with different Mk and clustercentric distance ranges for non-merging and merging host clusters . . . . . . . . . . . . . . . . . .. 5.1. 65. Total number of galaxies with Mk > -24.8 and clustercentric distance ranges for host clusters with or without X-ray detection . . . . . . . . . . . . . . .. 4.4. 61. 95. Total number of absorption-line AGN (AA) and galaxies from the 6dFGS galaxy sample in different clustercentric distance ranges . . . . . . . . . . 101. 6.1. Properties of radio galaxies in S0721 . . . . . . . . . . . . . . . . . . . . . 114. 6.2. Estimated mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118. xiii.

(19) xiv. LIST OF TABLES.

(20) Chapter 1 Introduction 1.1. Effects of Cluster Mergers on Member Galaxies. In a hierarchical universe, clusters grow through accreting and merging galaxies from groups, subunits or less dense environments. Mergers of clusters are dramatic events, releasing about 1064 ergs of energy on a timescale of Gyr. On cluster-wide scales, mergers lead to the appearance of shocks, radio halos and relics, as well as variations in temperature and spatial distribution of the intracluster medium (ICM). Such a violent event may have effects on their member galaxies, but for instance, it is still controversial in observations that how galaxy activities would be affected. As the radio investigations of cluster mergers showed that the fractions of galaxies to be radio sources appear to be enhanced in some mergers, such as A2125 (Dwarakanath & Owen 1999) and A2255 (Miller & Owen 2003), and appear normal in some other mergers like A3528 (Venturi et al. 2001) and A3571 (Venturi et al. 2002), and even reduced in A3558 (Venturi et al. 2000; 2003; Miller 2005). In addition, as shown in star formation activity of mergers, the evidence for an enhanced star formation activities was detected in the region between two substructures of mergers, such as A3921(Ferrari et al. 2005) and A168 (Hwang & Lee 2009), however, no enhancement was detected in some other clusters, like A1750 (Hwang & Lee 2009), RX J0152.7-1357(Marcillac et al. 2007) and MACS J0025.4-1225 (Ma et al. 2010). The different results may come from the related cluster merging stages and the properties of the galaxy members. For the merging stages, the timescale for virialization of one 1.

(21) 2. Chapter 1 Introduction cluster merger is about a few Gyr, but the timescale associated with events of star-burst or AGN is only about an order less than that of cluster mergers (Blundell & Rawlings 2000; Shabala et al. 2008), therefore the enhanced galaxy activity may only exist at some specific stage during cluster merging (e.g. Venturi et al. 2002; Emonts et al. 2006; Hwang & Lee 2009).. 1.2. Cluster Environmental Effects on Galaxy Activities. As to the properties of galaxy members, the effects of mergers on star-forming galaxies or AGN may be quite different. However, the fuel supply is the most important factor in triggering galaxy activities. For galaxies in cluster environments, they may have been preprocessed while they are in less dense environments during the formation of large-scale structure (e.g. Zabludoff & Mulchaey 1998). Several environmental processes such as strangulation (Larson et al. 1980; Kawata & Mulchaey 2008), ram-pressure stripping (Gunn & Gott 1972; Farouki & Shapiro 1980) and galaxy-galaxy interactions (merger and harassment (Moore et al. 1996)) have been proposed to be the mechanisms to alter the properties of galaxies . For these processes, strangulation is caused by the tidal force created by gravity of clusters, it is effective already while galaxies are still in cluster outskirts, it can remove the envelope gas and cut off the replenishment of cold disk gas needed for star formation, the time scale of this process is a few Gyr (Bekki et al. 2002). In the dense ICM regions (including shock fronts created by cluster mergers), ram-pressure is suggested to compress the molecular clouds in gas-rich galaxies and induce star-bursts (Roettiger et al. 1996; Bekki & Couch 2003; Bekki et al. 2010), or on the other hand, to stripe the gas of galaxies and thus shut down star formation (Fujita et al. 1999; Bekki 2009). As to the galaxy-galaxy interactions, the galaxy-galaxy mergers or close encounters can lead to gas transports, and thus trigger star formation (Moore et al. 1998) or AGN activity (Bahcall et al. 1997), and consume the gas reservoir. Therefore, during the formation of large scale structure, galaxies in the cosmic web may experience a wide variety of environments from filaments to galaxy groups, clusters, through cluster/group mergers. During this process, star formation activity may be triggered in some specific environments, but while the gas content is consumed by.

(22) 1.3 Galaxy Star Formation Activity in Outskirts of Clusters these environmental effects, the star formation activity may cease finally.. 1.3. Galaxy Star Formation Activity in Outskirts of Clusters. Much of what we have learned about the galaxy activity and evolution are mostly based on observations of denser cluster regions, where galaxies could be mostly in the later stage of evolution driven by the environmental processes. However, in cluster outskirts, the situations are more complicated. As the observations of star formation activity indicate, the suppression of star formation activity can extend out to ∼ 2 − 4 times of virial radius in massive clusters (e.g. Balogh et al. 1998; von der Linden et al. 2010; Chung et al. 2011) as well as in groups (Rasmussen et al. 2012). The possible effects proposed to explain the suppression of star formation activity beyond the virial radius may come from the “pre-processing” of galaxies in infalling groups (Zabludoff & Mulchaey 1998) and the “overshooting” (backsplash) galaxies, which are cluster members being pushed onto highly elliptical orbits beyond virial radius after their first pericentric passage (Balogh et al. 2000; Gill et al. 2005; Bahé et al. 2013). However, in recent years, there is growing evidence which shows enhanced star formation activity in outskirts of clusters. For example, in the cluster mergers RX J0152.7-1357 (Marcillac et al. 2007) and MACS J0025.4-1225 (Ma et al. 2010), the ongoing starbursts are observed predominantly in the infalling galaxies. In filaments along which galaxies are falling into rich clusters, enhanced star formation was detected in the outskirts of clusters (e.g. Fadda et al. 2008; Porter et al. 2008). The enhanced star formation activity in filaments was found to be mostly related to dynamically unrelaxed clusters (Braglia et al. 2009; Mahajan et al. 2012). The possible mechanism which triggers the enhanced star formation activity in cluster outskirts is suggested from galaxy-galaxy interactions when galaxies are infalling into clusters (Mahajan et al. 2012, and references therein). These observations indicate the effects of cluster mergers on galaxy star formation activity may extend beyond the virial radius.. 3.

(23) 4. Chapter 1 Introduction About the situations in cluster outskirts, it is interesting to see both suppression and enhancement of star formation activity were discovered in this region. From studies in literatures, it seems that suppression is rather usual in clusters, while enhancement prefers unrelaxed clusters with galaxies infalling from filaments. Therefore, it would be an interesting subject to study more about the relation between cluster properties and galaxy star oration activity in cluster outskirts.. 1.4. The Motivation of This Thesis. In this thesis, we are first interested in what the effects of cluster mergers are on their member galaxies, but before answer this question, it is important to understand the properties of galaxies involved in cluster mergers. For galaxies in the cosmic web, they may be born in the filaments, then infall into small groups, and follow a series of cluster/group mergers, finally reside in dense clusters; or they may infall into a rich cluster directly along the connected filaments, and enter cluster inner regions gradually. In the former situation, galaxies may experience diverse environments with growing host cluster/group halo mass, ICM density, surrounding galaxy density and cluster/group merger effects. In the later situation, galaxies may experience increasing galaxy and ICM densities while infalling towards cluster centers. Although the environmental effects on galaxy activities have been studied widely in literatures, it seems rare to have a comprehensive view of the relations between galaxy star formation activity and the environmental effects, which include cluster/group halo gravity, the ICM ram-pressure, galaxy-galaxy interactions, and cluster/group mergers, from filaments, galaxy groups to massive clusters. Therefore, to have such a comprehensive analyses is the major purpose of this thesis.. 1.5. The Shapley Supercluster. For this purpose, the Shapley supercluster (SSC) provides us the best laboratory, since it hosts a wide variety of environments from filaments, galaxy groups, to massive clusters, and the groups/clusters are mostly connected by filamentary structures. In this dense region,.

(24) 1.6 Outline of This Thesis a majority of cluster mergers at different dynamic states have been reported (e.g. Venturi et al. 2001; 2002; Ho & Chen 2008; Rossetti & Molendi 2010). Therefore, by using galaxy clusters/groups identified in this region, the relations between galaxy star formation activity and the properties of their host clusters/groups can be analyzed by dividing clusters/groups into populations with differences in halo mass, velocity dispersion, X-ray flux and merger features. Previous studies in the SSC focused majorly on three massive cluster mergers A3558, A3528 and A3571 complexes, as studied by radio source fractions of member galaxies, these merger complexes show different radio activities and were suggested to result from the different stages of mergers (Venturi et al. 2001; Mauduit & Mamon 2007). In the core of Shapley supercluster, the A3558 complex, attracts more attentions, the dynamic states of clusters and star formation activity in this region are studied by observations from radio, infrared, optical, to X-ray wavelength (e.g. Bardelli et al. 1994; Kull & Böhringer 1999; Finoguenov et al. 2004; Miller 2005; Haines et al. 2011). From these studies, the clusters in this complex are suggested to have experienced cluster mergers, and the major star-forming galaxies detected here are suggested to be fainter galaxies infalling into the cluster environment for the first time (Haines et al. 2011). The Shapley supercluster is located at 0.03 ≤ z ≤ 0.06, 12h40m≤ RA ≤14h00m and -40◦ ≤ Dec ≤ −22◦ .. 1.6. Outline of This Thesis. The outline of this thesis is as follows: the data sets used in this thesis is introduced in chapter 2. In chapter 3, the properties of galaxy clusters and groups in the SSC are summarized. The cluster properties include σv , r200 , M200 , number of member galaxies, DS-test probability and cluster/group ellipticity. The alignments of clusters in the SSC are analyzed here. In chapter 4, by using 4000 Å break strength (D4000) as the indicator of mean stellar age of galaxies, the character of D4000 in the SSC and relations of D4000–radius for galaxies with different host cluster/group properties are analyzed. In chapter 5, by using radio selected star-forming galaxies (SFG) and absorption-line AGN (AA), the relations of fSFG –density ( fAA –density) as well as relations of fSFG –radius ( fAA –radius) for galaxies. 5.

(25) 6. Chapter 1 Introduction with different host cluster/group properties are analyzed. In chapter 6, we study the cluster dynamical state of one cluster merger in the SSC — Abell S0721, and investigate the possible connection between the cluster dynamical state and the properties of its member galaxies. A Hubble constant of value H0 = 70 km sec−1 Mpc−1 , Ωλ = 0.7, and ΩM = 0.3 are used through this thesis..

(26) Chapter 2 Data 2.1. Data Catalogues. For the purpose to investigate the environmental effects on galaxy activities across the SSC, it is essential to have the data sets more complete and homogenous. In this study, several survey catalogues in different wavelengths are used, including the Two Micro All Sky Survey (2MASS), Six-degree Field Galaxy Survey (6dFGS), NRAO VLA Sky Survey ( NVSS), ROSAT All Sky Survey (RASS), ROSAT-ESO Flux Limited X-ray (REFLEX) cluster catalogue, and redshift data from the NASA Extragalactic Database (NED). Brief descriptions of these catalogues as well as the analyses of data completeness and correction are shown below .. 2.1.1. Two Micro All Sky Survey. 2MASS is a ground-based, all-sky survey that utilized the near-infrared band in J (1.24 ), H (1.66 ) and K (2.16 ). The 2MASS All-Sky Extended Source Catalogue (XSC; Jarrett et al. (2000)) contains over 1.6 million resolved sources, which have similar high standards of uniformity, completeness and reliability. The completeness at S/N = 10 flux limit of K ∼ 13.5 mag is greater than 90%. (Skrutskie et al. 2006). The completeness of XSC is 92.2% for K ≤ 13.57 by cross-correlaton with galaxies from the Sloan Digital Sky Survey (SDSS) main galaxy sample (MGS)(McIntosh et al. 2006). 7.

(27) 8. Chapter 2 Data The 2MASS data also provides an accurate estimation of stellar mass, it is due to that near-infrared wavelengths are sensitive to old stellar populations that dominate galaxy masses, and are not affected by recent star formation. Furthermore, the extinction (both internal and Galactic) is much less than at optical wavelengths. Therefore, the stellar massto-light ratios are more tightly correlated than at optical (Bell & de Jong 2001). A total of 17737 sources are drawn from the 2MASS XSC in the SSC area, of which 9547 sources have K band total mag brighter than 13.5.. 2.1.2. Six-degree Field Galaxy Survey. The 6dF Galaxy Survey (Jones et al. 2004; 2009) is a near-infrared-selected spectriscopic survey over the southern sky (|b| > 10◦ ). Its 136 304 spectra have yielded 110 256 new extragalactic redshifts and a new catalogue of 125 071 galaxies making near-complete samples with (K, H, J, rF , bJ ) ≤ (12.65, 12.95, 13.75, 15.60, 16.75), the median redshift is 0.053. This survey was carried out on the UK Schmidt telescope (UKST) using the Six-degree Field (6dF) multi-object fibre spectrograph from 2001 to 2006. Most 6dFGS spectra consist of two parts, observed separately through different gratings, and subsequently spliced together. The wavelength coverage are 3900-5600 Å and 5400-7500 Å, for R and V, respectively. (Data taken prior to October 2002 used different gratings, spanning 4000-5600 Å and 5500-8400 Å.) The fibre diameter of 6dFGS is 6.7 arcsec, which correspond to a projected diameter of 6.6 kpc at z=0.05 (the center of SSC). The spectrum data used in this study is obtained through the website at http://wwwwfau.roe.ac.uk/6dFGS, the accessed data including images, spectra, photometry and redshifts, only the reliable spectra with Q=3 or Q=4 are selected here. A total of 3826 galaxies are in the SSC area, of which 2904 galaxies are members of the SSC.. 2.1.3. NRAO VLA Sky Survey. The NRAO VLA Sky Survey (NVSS; Condon et al. (1998)) is a 1.4 GHz continuum survey covering the entire sky north of -40 deg declination . The principal data products are a set of 2326 4 × 4 continuum images with 45 arcsecond FWHM angular resolution, and a catalogue.

(28) 2.1 Data Catalogues of about 2 million discrete sources. The rms uncertainties in position vary from < 1 arcsec for relatively strong (S > 15 mJy) point sources to greater than 7 arcsec for the faintest sources at the survey limit. The completeness limit is about 2.5 mJy. The NVSS images and sources were queried through internet, the version of source catalogue was updated in June 2009. A total of 15642 sources are compiled in the SSC area.. 2.1.4. ROSAT All Sky Survey and ROSAT-ESO Flux Limited X-ray (REFLEX) Cluster Catalogue. The RASS is the first X-ray all sky survey in the soft X-ray band (0.1-2.4 keV) with an imaging X-ray telescope. The images of RASS III (third re-processing) dataset are accessible from ROSAT data archive (http:// www.xray.mpe.mpg.de/cgi-bin/rosat/data-browser), the mean exposure time of the SSC area is about 300 seconds. The REFLEX cluster catalogue (Böhringer et al. 2004) is a statistically complete X-ray flux-limited sample of 447 galaxy clusters above an X-ray flux of 3 × 10−12 erg s−1 cm−2 (0.1 to 2.4 keV) in an area of 4.24 ster in the southern sky. The cluster candidates were first selected by their X-ray emission in the ROSAT-All Sky Survey and subsequently spectroscopically identified in the frame of an ESO key programme. This catalogue is accessible through http://www.xray.mpe.mpg.de/theorie/REFLEX/DATA. A total of 16 clusters are located in the SSC. In addition to REFLEX catalogue, in study of de Filippis et al. (2005), also based on the RASS data(RASS-III), they performed an X-ray survey of a wide region surrounding the SSC. By adopting a lower flux limit of fX (0.1−2.4 keV) = 1.55 ×10−12 erg cm−2 s−1 , they identified 26 clusters in their study region, of which six are under the detection of REFLEX and located in our study region (the SSC region surveyed by de Filippis et al. (2005) is wider than our study region).. 9.

(29) 10. Chapter 2 Data. 2.1.5. Velocity data from the NASA Extragalactic Database. The galaxy velocity catalogue is acquired from the NED, there have been several surveys performed in the SSC area for different scientific purposes. A total of 7440 galaxies are observed in the SSC area with z ≤ 0.1, of which 4829 are members of the SSC. These data are majorly from 6dF galaxy survey final redshift release (6dFGS DR3) (Jones et al. 2009), FLAIR Shapley-Hydra (FLASH) redshift survey (Kaldare et al. 2003), and observations of Bardelli et al. (1994; 1998; 2000; 2001), Quintana et al. (1997) and Drinkwater et al. (1999). These observations are majorly carried out on the UKST, the equipped spectrograph was 6dF multi-object fibre spectrograph for 6dFGS, and FLAIR-II fibre spectrograph for FLASH redshift survey and Drinkwater et al. (1999). The observations of Bardelli et al. (1994; 1998; 2000; 2001) and Quintana et al. (1997) were obtained by using the ESO 3.6-m telescope in La Silla, the multifibre spectrograph used in observations of Bardelli et al. (2000) and Quintana et al. (1997) was MEFOS, and OPTOPUS for the others. The magnitude ranges span differently for theses surveys, for 6dFGS, it is near complete to (K, H, J, rF , bJ ) ≤ (12.65, 12.95, 13.75, 15.60, 16.75), for FLASH and observations of Bardelli et al., they are bJ ≤ 16.7 and 17.0 < bJ < 18.8 , respectively. Although the velocity data compiled from NED were observed by different instruments, but according to the studies of Quintana et al. (2000) and Proust et al. (2006), the relative mean velocity differences (zero-point shifts) among 6dFGS, FLASH and observations of Bardelli et al. are small, they fall mostly within 15 km s−1 , in comparison with the rms scatter of 66 km s−1 for 6dFGS and 95 km s−1 for FLASH, the velocity differences are negligible..

(30) 2.2 Galaxy Velocity Catalogue, Completeness and Galaxy Distribution. 2.2. Galaxy Velocity Catalogue, Completeness and Galaxy Distribution. 2.2.1. Velocity catalogue. The velocity sample used in this study is first compiled from the NED, it is combined of several surveys based on different selection criteria. To have a more complete and uniform velocity catalogue, a parent catalogue of 9547 sources drawn from the 2MASS XSC with total K band mag less than the completeness limit K = 13.5 are used for further completeness analyses and correction, . In this study, K = 13.5 is taken as the limit magnitude for statistical analyses. The 7440 galaxies in the velocity sample are cross-correlated with the 2MASS parent catalogue with a matching radius 3" to select galaxies with K ≤ 13.5, a total of 4895 counterparts are detected. The velocity distribution of galaxies is shown in Figure 2.1, black and red lines represent the whole velocity sample and those with K ≤ 13.5, respectively. The fraction of velocity sample with counterparts in the parent 2MASS catalogue is lower around 15000 km s−1 , this is due to the deeper observations for richer clusters located around this redshift.. 2.2.2. Data completeness. The distribution of 9547 galaxies in the parent 2MASS catalogue is complete to K = 13.5 and uniform across the SSC projected plane. As to the radial distribution, only 5323 of them have velocity measured. The completeness of the velocity catalogue is analyzed on basis of the parent 2MASS galaxy catalogue. The distributions of K band magnitude of sources from 2MASS XSC and velocity sample towards the SSC are shown in Figure 2.2, the completeness of velocity observations is higher for the brighter sources, and an obvious drop occurs at K = 12.5. The completeness distribution in the projected plane is shown in Figure 2.3, here the completeness in a pixel is defined as the fraction of galaxies in the parent catalogue that have measured velocities in the velocity catalogue. It is obvious to see that the completeness across the SSC area is not uniform, it is nearly complete in rich cluster. 11.

(31) 12. Chapter 2 Data. Figure 2.1 Velocity distribution of galaxies towards the SSC with 0 ≤ v ≤ 30000 km s−1 , black and red lines represent the full velocity sample from the NED and those with K ≤ 13.5, respectively, bin size is 500 km s−1 ..

(32) 2.2 Galaxy Velocity Catalogue, Completeness and Galaxy Distribution regions, and less complete for field regions.. Figure 2.2 Distribution of K band magnitude for sources from 2MASS XSC (black) and velocity sample (red), with a bin size of 0.5 mag. The dotted line represents the limiting magnitude 13.5.. To deal with the problem of incompleteness and inhomogeneity in velocity observations, here we assume that within a specified sky projected area, the fraction of galaxies whose velocities are within a specified velocity range is similar to that in the parent catalogue. Therefore, by using the velocity catalogue, this fraction could be calculated as the ratio of the number of galaxies with measured velocities within the specified range to the total number of galaxies in the same area. Hence the total number of galaxies in this cylindrical volume with the specified sky area and radial velocity range could be estimated by the total number of galaxies in the parent catalogue multiplied by this fraction factor. That. 13.

(33) 14. Chapter 2 Data. Figure 2.3 Fraction of galaxies in the parent 2MASS catalogue that have measured velocities in the velocity catalogue with magnitude limit K = 13.5, pixels in black color represent no galaxy inside. The superimposed contours are galaxy number density of the SSC at 3, 4, 8,16 and 32σ levels . Each pixel is 5 × 5 arcmin2 ..

(34) 15. 2.2 Galaxy Velocity Catalogue, Completeness and Galaxy Distribution is, in a projected sky area,. f∆V = N∆V,vcat /Nvcat ,. (2.1). where f∆V is the fraction of galaxies whose velocities are within a specified velocity range, N∆V,vcat is the number of galaxies in velocity catalogue with velocities in the specified range, and Nvcat is the total number of galaxies in velocity catalogue.. N∆V,parent ' N parent × f∆V ,. (2.2). where N∆V,parent is the number of galaxies in parent catalogue with velocities in a specified range, and N parent is the total number of galaxies in 2MASS parent catalogue. However, this number estimation is based on the assumption that velocity distributions are similar in both parent and velocity catalogues, for regions with poor sampling rate, this estimation will induce larger bias, and the uncertainty need to be considered.. 2.2.3. Galaxy distribution. The velocity distribution of galaxies towards the SSC in right ascension and declination is shown in Figure 2.4. It is clear to see there are several connected dense clumps in the SSC (9000-18000 km s−1 ), the most concentrated regions are around 15000 km s−1 , and the feature of finger-of-God appear clearly in these dense regions. As to the galaxy distribution on the sky, the projected distribution of galaxies towards the SSC from the parent catalogue is shown in Figure 2.5. The true galaxy number density distribution of the SSC members can be estimated by applying a correction factor ( f∆V ) to the distribution from parent catalogue (see section 2.2.2 for detail). For each pixel in the figure, the fraction of galaxies that belong to the SSC with 9000 ≤ v ≤ 18000 km s−1 in the velocity catalogue is shown in Figure 2.6, the number of SSC member galaxies in each pixel is estimated by the multiplication of the total number in parent catalogue times the correction fraction ( f∆V ). Based on this estimation, the distribution of SSC members is plotted in Figure 2.7 (upper), for reducing the possible projection effect, the velocity range.

(35) 16. Chapter 2 Data. Figure 2.4 Wedge diagrams in right ascension (top) and declination (bottom) for galaxies with K ≤ 13.5 towards SSC are plotted in radial velocity coordinate. Galaxies with velocities in the range 9000-18000 km sec−1 (red dotted line) are belonged to SSC . The angles in wedge diagrams are expanded by a factor ∼ 2 for clarity..

(36) 2.2 Galaxy Velocity Catalogue, Completeness and Galaxy Distribution is split into two slices which have 9000 ≤ v ≤ 13500 km s−1 and 12000 ≤ v ≤ 18000 km s−1 respectively, the distributions are shown in Figure 2.7 (bottom).. Figure 2.5 Distribution of projected galaxy number density from 2MASS parent catalogue on the sky, each pixel is 5 × 5 arcmin2 .. 17.

(37) 18. Chapter 2 Data. Figure 2.6 Fraction of galaxies that belong to the SSC with 9000 ≤ v ≤ 18000 km s−1 in velocity catalogue, pixels in black color represent no galaxy inside. The superimposed contours are galaxy number density of the SSC at 3, 4, 8,16 and 32σ levels. Each pixel is 5 × 5 arcmin2 ..

(38) 2.2 Galaxy Velocity Catalogue, Completeness and Galaxy Distribution. Figure 2.7 Distribution of estimated galaxy number density within 9000 ≤ v ≤ 18000 (upper), 9000 ≤ v ≤ 13500 (bottom left) and 12000 ≤ v ≤ 18000 (bottom right), each pixel is 5 × 5 arcmin2 .. 19.

(39) 20. Chapter 2 Data.

(40) Chapter 3 Properties of Galaxy Clusters and Groups in the SSC 3.1. Compilation and Identification of Galaxy Clusters and Groups. 3.1.1. Galaxy clusters and groups compiled from the NED. The galaxy cluster/group catalogue of the SSC used in this study is based on those compiled from the NED. However, since the galaxy clusters and groups compiled from the NED include results from different observations and detection algorithms, and thus one cluster/group may be detected by different observations more than one time, or it is just a substructure of one larger cluster. We therefore discard those detected as substructures first. In addition, previous cluster/group identifications based on the optical images may lacked galaxy redshift data, therefore the centers of clusters might be defined by foreground or background bright galaxies and lead to the bias in cluster centers and redshifts. Therefore, in order to confirm the cluster/group uniqueness and calculate the basic properties of clusters/groups such as virial radius and mass, all galaxies with measured velocity (∼ 5000 galaxies in the SSC) as well as X-ray observations in this region are used to establish the cluster/group catalogue used in this study.. 21.

(41) 22. Chapter 3 Properties of Galaxy Clusters and Groups in the SSC. 3.1.2. X-ray detected galaxy clusters and groups. The X-ray detections of clusters/groups in the SSC are compiled from the REFLEX cluster catalogue (Böhringer et al. 2004) and the study of de Filippis et al. (2005). A total of 16 clusters from the REFLEX cluster catalogue with X-ray flux (0.1 − 2.4 keV) above 3 × 10−12 erg s−1 cm−2 and the additional 6 clusters from de Filippis et al. (2005) with X-ray flux (0.1 − 2.4 keV) above 1.55 ×10−12 erg cm−2 s−1 are compiled. The measured and estimated X-ray flux, luminosity and temperature of clusters are listed in 3.1. The X-ray flux and luminosity are quoted from the REFLEX catalogue and the Table 4 of de Filippis et al. (2005), while the cluster temperature is surveyed through “BAX” (The X-Ray Galaxy Clusters Database, http://bax.ast.obs-mip.fr/). For those with temperature estimated from the spectroscopic data, the temperature is quoted from the related literatures, as to those without spectroscopic data, the cluster temperature is derived through the Lx − T relation from Markevitch (1998): kT = 6 [keV]. 3.1.3. ! 1 Lx 1044 erg s−1 2.10 . 1.41 h−2. (3.1). Detection of unidentified galaxy groups. To identify galaxy systems which have not yet been detected before, the galaxy distribution in the SSC is binned with a pixel size of 3 × 3 arcmin2 by using equations 2.1 and 2.2. These binned pixels are further smoothed by convolving with a 3 × 3 Gaussian kernel with FWHM of 6 arcmins. The galaxy density fluctuation σ is estimated by the standard deviation of background galaxy density distribution. The overdensity regions are defined as groups of pixels which have density greater than 3σ . These pixels above the threshold are linked with each other in case of i ± 1 or j ± 1, where i and j are pixel index number in RA and Dec directions, respectively. It is similar to the method of friend-of-friend, all linked pixels are belonged to the same overdensity region, that is, one galaxy system candidate. The centers of galaxy system candidates are defined by the density peak of overdensity regions, and the redshifts are determined preliminarily by the mean velocity of galaxies in overdensity regions..

(42) 23. 3.1 Compilation and Identification of Galaxy Clusters and Groups. Table 3.1 Properties of X-ray detected clusters in the SSC Name. RA. Dec. z. fx (0.1-2.4 keV). Lx (0.1-2.4 keV). kT. 10−12 erg cm−2 s−1. 1044 erg s−1. keV. Ref.. *. RBS1175. 193.1421. -31.2678. 0.0535. 12.91. 1.013. 3.65. *. A3528N. 193.5979. -29.0228. 0.0542. 8.801. 0.727. 4.65. b. *. A3528S. 193.6725. -29.2233. 0.0544. 15.402. 1.196. 4.94. a. *. A3530. 193.8938. -30.3306. 0.0541. 10.314. 0.741. 3.68. b. *. BS(RXCJ1256.9-3119). 194.2492. -31.3219. 0.0561. 5.378. 0.422. 2.41. *. A3532. 194.3204. -30.3769. 0.0554. 18.733. 1.457. 4.34. *. S0721. 196.4771. -37.6614. 0.0497. 8.181. 0.495. 2.6. *. A1736. 201.7061. -27.1634. 0.0458. 36.893. 1.796. 2.95. c. *. A3558. 201.9896. -31.5025. 0.0480. 58.526. 3.518. 5.51. a. *. A3558(B)(SC1327-312). 202.4288. -31.6025. 0.0488. 14.434. 0.865. 3.53. a. *. A3558(C)(SC1329-314). 202.885. -31.8153. 0.0448. 4.901. 0.257. 1.9. *. A3560. 203.0942. -33.1394. 0.0487. 14.129. 0.833. 3.3. d. *. A3562. 203.4012. -31.6611. 0.0490. 24.485. 1.475. 3.8. a. *. A3570. 206.7188. -37.8744. 0.0377. 5.527. 0.191. 2.3. b. *. A3571. 206.8683. -32.8497. 0.0391. 115.471. 4.206. 7.6. a. *. BS(A3577). 208.3721. -27.8886. 0.0468. 4.993. 0.281. 1.98. +. S0718. 194.963. -33.661. 0.0478. 1.43. 0.073. 1.1. +. S0724. 198.286. -32.994. 0.0493. 2.05. 0.111. 1.3. +. A3553. 199.805. -37.179. 0.0487. 1.35. 0.071. 1.1. +. A3554. 199.865. -33.497. 0.0470. 2.91. 0.143. 1.5. +. S0729. 200.358. -35.816. 0.0499. 1.27. 0.071. 1.1. +. A3556. 201.001. -31.656. 0.0479. 1.72. 0.088. 3.8. b. b. “*” : X-ray detection by REFLEX; “+”: X-ray detection by de Filippis et al. (2005). Ref: literature reference for the cluster temperature: a (Cavagnolo et al. 2009), b (Fukazawa et al. 2004), c (Vikhlinin et al. 2009), d (de Plaa et al. 2007)..

(43) 24. Chapter 3 Properties of Galaxy Clusters and Groups in the SSC All candidates are further cross-correlated with the known clusters/groups, for those without identified counterpart, they are suggested to be new identification candidates. All new identification candidates need to be examined by the iterative method described below.. 3.1.4. Determination of velocity dispersion σv , r200 , M200 , and cluster members. For clusters and groups compiled from the NED or our new identifications, the virial radius and virial mass are derived through the calculation of r200 and M200 . The definition of r200 is the radius inside which the density is 200 times the critical density, and M200 is the total mass inside of r200 : 3 M200 = 200 ρc × 4/3 r200 ,. (3.2). where r200 approximates the virial radius, and thus M200 approximates the virial mass. In this study, the r200 and M200 of 22 X-ray detected clusters are derived through the relation of M500 − Tx from Vikhlinin et al. (2009): 14. . M500 = (2.95 ± 0.10) × 10 where E (z) =. kB Tx 5keV. 1.5. h−1 E (z)−1 M

(44) ,. (3.3). q. ΩM,0 (1 + zcl )3 + ΩΛ , and the halo mass is estimated by M200 = 2.1M500. (Muñoz & Loeb 2008). As to the clusters/groups under X-ray detection, r200 are estimated by cluster velocity dispersion σv of cluster members within r200 and ±3σv of cluster redshift zcl (Finn et al. 2005): r200 = 1.73. σv q 1000 km s−1 Ω. 1. h−1 Mpc. 3. M,0 (1 + zcl ). (3.4). + ΩΛ. The determination of velocity dispersion σv and r200 for one cluster is through an iterative algorithm : 1. For clusters/groups from the NED, the cluster centers and redshifts are first defined as those from the NED, and the initial searching radius is10 arcmins, all galaxies within this radius and have radial velocity within ±3000 km s−1 of the cluster redshift zcl are selected..

(45) 3.1 Compilation and Identification of Galaxy Clusters and Groups 2. The new redshift zcl , velocity dispersion σv , and cluster virial radius r200 are estimated by the galaxies selected by step (1) through equation 3.4, where σv is limited to be less than 300 km s−1 to exclude severe contamination from foreground and background galaxies. 3. By using the biweight estimator from Beers et al. (1990), the zcl , σv , and r200 are estimated by the member galaxies (at least 4 galaxies) within r200 and ±3σv of zcl iteratively until convergence is reached, i.e. subsequent iterations differ by less than p 0.03× 0.5/(n − 1) in σv , where n is the total number of cluster members with n ≥ 4. For each cluster/group has estimated zcl , σv and r200 through these steps, it is further visually examined by the distribution of member radial velocities, and the image of galaxy density distribution. If one cluster/group has its members mostly lie within r200 of other richer cluster, then it is taken as a substructure of this richer cluster and is discarded. Furthermore, we also find that the centers of A3537 and A3541 quoted from the NED were defined by foreground bright galaxies, therefore we redefined their centers by mean RA and Dec of the cluster members, where the center of A3537 is from (195.261, -32.436) to (195.506, -32.601), and that of A3541 is from (197.171, -34.567) to (197.161, -34.430 ). In addition, for A3568, there have no cluster members within ∼ 12 arcmins of the center quoted from the NED, therefore the center of this cluster was redefined by a nearby overdensity region at the similar redshift, from (205.296, -34.636) to (205.346, -34.388). For these clusters, the zcl , σv and r200 were estimated again by adopting the new centers. For X-ray detected cluster RBS 1175, we also found the estimated r200 and M200 from the X-ray luminosity is much larger than that estimated by the velocity dispersion σv , and is inconsistent with the small total number of cluster members from both the velocity and 2MASS catalogues. The possible explanation for this inconsistence is that the X-ray flux of this cluster is contaminated by three faint X-ray point sources. Therefore, the r200 and M200 of this cluster was calculated through σv . After removing the clusters/groups which have less than 4 members and those are taken as substructures, a total of 52 clusters and groups from the NED and 17 new identifications are adopted in this study. The galaxy density distribution and the adopted clusters/groups in. 25.

(46) 26. Chapter 3 Properties of Galaxy Clusters and Groups in the SSC the SSC are shown in Figure 3.3, where the clusters/groups from the NED and new identifications in this study are represented by the yellow and red circles with a radius of r200 , respectively.. 3.2. Dynamic States of Galaxy Clusters and Groups. In this study, only a few clusters which have deep X-ray observations, in order to identify clusters/groups which are on-going mergers, we use the DS-test (Dressler & Shectman 1988) and cluster ellipticity as indicators of cluster/group dynamical states.. 3.2.1. DS-test probability of galaxy clusters and groups. The DS-test is a three dimensional substructure test, which is used to test the reality of cluster substructures. This test was analyzed as the most sensitive test in 31 statistic tests in the study of Pinkney et al. (1996). However, it is insensitive in situation where the substructures are well superimposed. The algorithm of DS-test computes the deviation (δ ) of global mean radial velocity v¯ and velocity dispersion σ from all cluster members and local value (v¯local and σlocal ) from each galaxy and its Nnn nearest neighbors, here we adopt Nnn = N 1/2 (Lopes et al. 2009) instead of Nnn =10 in the study of Dressler & Shectman (1988), where N is the total galaxy number within cluster r200 , and with N ≥ 5. The deviation (δ ) is defined as δ 2 = (Nnn + 1)/σ 2. i h (v¯local − v) ¯ 2 + (σlocal − σ )2 ,. (3.5). the sum of δ for N cluster members is defined as ∆. For substructure test itself has little meaning if not properly normalized, therefore we should compare the results with substructurefree samples (the null hypothesis) by simulations. The significance level of substructure is determined through comparing with 1000 Monte Carlo simulations, where galaxy positions are fixed and the velocities are randomly assigned (keep the same histogram distribution). For simulations with ∆sim ≥ ∆real mean they show more substructures than the real data. The DS-test probability is computed as.

(47) 3.2 Dynamic States of Galaxy Clusters and Groups. Figure 3.1 Distribution of DS-test probabilities for clusters/groups in the SSC, those with X-ray detections are denoted by red histogram. Each bin is 0.05.. the number of simulations with ∆sim ≥ ∆real divided by the total number of simulations, that is, a high probability means the substructures in a cluster is possibly by chance, and thus a lower probability means the substructures are possibly real. The DS-test probability distribution of the clusters in the SSC is shown in Figure 3.1. In this study, the probability of 0.05 is set as the significance threshold for cluster mergers (Lopes et al. 2009).. 3.2.2. Ellipticities of galaxy clusters and groups. The cluster/group shape is estimated by using the moments of inertia method (Basilakos et al. 2000) through a smoothed galaxy distribution on a grid, the steps are: 1. All galaxies with K ≤ 13.5 and within 2r200 are selected from the velocity and 2MASS catalogues. 2. The galaxy distribution is binned with a pixel size of 3 × 3 arcmin2 , and for each pixel, the number of galaxies is calculated by using equation 2.1 and 2.2. This grid is then. 27.

(48) 28. Chapter 3 Properties of Galaxy Clusters and Groups in the SSC smoothed by convolving a 3 × 3 Gaussian kernel with FWHM of 6 arcmin. 3. Pixels within r200 and with galaxy density greater than 3σ are selected for ellipticity calculation. 4. For each selected pixel, the distance from the center of pixel to the center of cluster in RA is xi = (RAi − RAcl )×cos(δcl ), and in Dec is yi = δi − δcl , where subscripts i and cl refer to the selected pixel and the cluster, respectively. 5. The moments are evaluated as: I11 = ∑ wi xi2 , I22 = ∑ wi y2i , I12 = I21 = ∑ wi xi yi , where wi is the total galaxy number in each pixel. By diagonalizing the inertia tensor det(I − λ 2 M2 ) = 0, where M2 is a 2 × 2 unit matrix, the eigenvalues λ1 , λ2 are used for defining the apparent ellipticity of cluster by: ε = 1 − λ2 /λ1 , with λ1 > λ2 . The corresponding eigenvector provides the direction of the major axis. Although the apparent ellipticities are calculated by the projected galaxy distributions, according to the scenario that the growth of clusters is through accretion of smaller units along the filaments, the shapes of clusters are more similar to prolate spheroids (Basilakos et al. 2000). The projected ellipticity of one merging cluster is the same as the intrinsic one if the merger occurs in the direction of the projected sky, and is much smaller if the merger occurs along the line of sight. Therefore, for clusters/groups with large apparent ellipticities, their intrinsic ellipticities are even larger, and their elongated shapes indicate that they are possibly on-going mergers. The distribution of cluster apparent ellipticities is shown in Figure 3.2. In this study, the ellipticity of 0.6 is set as the threshold for cluster mergers..

(49) 3.3 Summary of Properties of Galaxy Clusters and Groups in the SSC. Figure 3.2 Distribution of cluster/group ellipticities in the SSC, those with X-ray detection are denoted by red histogram. Bin size is 0.1.. 3.3. Summary of Properties of Galaxy Clusters and Groups in the SSC. The properties of clusters and groups in the SSC are listed in Table 3.2. Those classified as galaxy clusters from the NED are listed first, and followed by the galaxy groups from the NED. Those detected by this study are listed in the final. It is noted that clusters are mostly identified by Abell et al. (1989) and X-ray observations, while groups from the NED are mostly identified by Ragone et al. (2006) and named by “SSGC”. The distribution of cluster redshifts zcl , velocity dispersion σv , M200 , and r200 are shown in Figure 3.4. The redshift distribution shows that most clusters/groups are located around z ' 0.05, and a smaller population is located at 0.03 < z < 0.04. For the distributions of σv , M200 , and r200 , the clusters with X-ray detections (overplotted by red lines) have higher values, however, the separation between those with X-ray detections and without X-ray detection is not very clear.. 29.

(50) 30. Chapter 3 Properties of Galaxy Clusters and Groups in the SSC. Figure 3.3 Distribution of estimated galaxy number density in the SSC, A total of 69 clusters and groups belonging to the SSC are denoted by circles with a radius of r200 , those with red color are groups identified in this study. The pixel size is 5 × 5 arcmin2 ..

(51) 3.3 Summary of Properties of Galaxy Clusters and Groups in the SSC. Figure 3.4 Distribution of the cluster redshifts zcl (upper left), velocity dispersions σv (upper right), M200 (lower left), and r200 (lower right) for clusters/groups in the SSC. For the X-ray detected clusters/groups, their r200 and M200 are calculated through temperature or X-ray luminosity from the X-ray observations, while for those under X-ray detection, theirs are calculated through velocity dispersions.. 31.

(52) 32. Table 3.2 Properties of galaxy clusters/groups in the SSC name. RA. Dec. (Deg). (Deg). z. σv. M200. r200. (km s−1 ). (1014 M

(53) ). (Mpc). Nv. f. N2mass× f. DS-test. e. prob.. PA. cBCG. cX. (Deg). BCG AGN. RBS 1175. 193.1250. -31.2667. 0.0536. 370.1. 0.81. 0.89. 7. 1. 12. 0.724. 0.15. 86.7. 1. 1. 1. *. ABELL 3528N. 193.5921. -29.0128. 0.0538. 1025.8. 7.74. 1.89. 149. 0.78. 86.7. 0.042. 0.52. 166.1. 1. 1. 1. *. ABELL 3528S. 193.6692. -29.2289. 0.0542. 1014.7. 8.48. 1.95. 165. 0.71. 80.7. 0.043. 0.63. 168.3. 1. 1. 1. *. ABELL 3530. 193.9038. -30.3539. 0.0547. 750.4. 5.45. 1.68. 158. 0.93. 79.6. 0.069. 0.7. 92.2. 1. 0. 0. *. RXCJ1256.9-3119. 194.2492. -31.3219. 0.0556. 719.0. 2.88. 1.36. 41. 0.94. 36.5. 0.566. 0.42. 65.1. 1. 1. 1. *. ABELL 3532. 194.3300. -30.3703. 0.0553. 723.3. 6.98. 1.83. 158. 0.94. 93.4. 0.091. 0.58. 87.9. 1. 1. 1. +. ABELL S0718. 194.9371. -33.6694. 0.0474. 227.8. 0.89. 0.92. 8. 0.56. 8.9. 0.449. 0.15. 156.9. 1. 1. 0. ABELL 3537. 195.5055. -32.6011. 0.0313. 235.7. 0.22. 0.57. 8. 0.27. 9.5. 0.884. 0.58. 9.2. 0. 0. 0. ABELL S0721. 196.5250. -37.5842. 0.0495. 682.4. 3.23. 1.42. 42. 0.82. 32.7. 0.209. 0.63. 56.0. 1. 0. 1. ABELL 3542. 197.1610. -34.4296. 0.0506. 284.9. 0.37. 0.69. 6. 0.36. 4.7. 0.084. 0.67. 128.1. 0. 0. 0. ABELL S0724. 198.3208. -32.9481. 0.0508. 485.6. 1.14. 1.00. 5. 0.63. 9.4. 0.063. 0.62. 40.4. 0. 0. 0. ABELL S0726. 198.7992. -33.6475. 0.0484. 218.8. 0.17. 0.53. 5. 1. 8. 0.036. 0.52. 79.6. 1. 0. 0. ABELL 3552. 199.7225. -31.8128. 0.0521. 253.2. 0.26. 0.61. 7. 0.78. 8.6. 0.223. 0.08. 87.7. 1. 0. 0. +. ABELL 3553. 199.8108. -37.1792. 0.0505. 420.2. 0.89. 0.92. 19. 0.81. 25.1. 0.643. 0.54. 57.4. 1. 1. 1. +. ABELL 3554. 199.8767. -33.4792. 0.0490. 537.1. 1.42. 1.08. 21. 0.7. 28.5. 0.1. 0.34. 162.4. 1. 1. 0. *. +. Chapter 3 Properties of Galaxy Clusters and Groups in the SSC. *.

(54) name. RA. Dec. (Deg). (Deg). z. σv. M200. r200. (km s−1 ). (1014 M

(55) ). (Mpc). Nv. f. N2mass× f. DS-test. e. prob.. PA. cBCG. cX. (Deg). BCG AGN. +. ABELL S0729. 200.3842. -35.7950. 0.0502. 684.3. 0.89. 0.92. 20. 0.78. 32.1. 0.526. 0.43. 87.9. 1. 0. 1. +. ABELL 3556. 201.0258. -31.6606. 0.0477. 635.4. 4.18. 1.54. 178. 0.86. 61.9. 0.075. 0.62. 69.9. 1. 0. 1. ABELL 1736 NED01. 201.6846. -27.4394. 0.0349. 388.1. 0.96. 0.94. 31. 0.26. 21.1. 0.146. 0.3. 10.0. 1. 0. 1. *. ABELL 1736 NED02. 201.7029. -27.1439. 0.0442. 789.2. 4.00. 1.52. 130. 0.69. 95.2. 0.241. 0.31. 146.5. 1. 0. 0. *. ABELL 3558. 201.9783. -31.4922. 0.0480. 1033.7. 10.01. 2.06. 418. 0.96. 196.8. 0.000. 0.3. 112.0. 1. 0. 1. *. SC 1327-312. 202.4458. -31.6081. 0.0483. 1065.6. 5.12. 1.65. 340. 0.96. 155.8. 0.000. 0.7. 103.3. 1. 0. 0. ABELL 3559. 202.4746. -29.5247. 0.0476. 582.8. 3.20. 1.41. 47. 0.58. 27.8. 0.382. 0.32. 111.7. 1. 0. 1. ABELL S0736. 202.7467. -28.0408. 0.0334. 568.0. 3.01. 1.38. 36. 0.82. 37.1. 0.524. 0.69. 97.2. 1. 0. 0. *. SC 1329-314. 202.9000. -31.8128. 0.0465. 1119.0. 2.03. 1.21. 161. 0.97. 70.9. 0.007. 0.28. 101.1. 0. 1. 0. *. ABELL 3560. 203.1054. -33.1367. 0.0490. 831.6. 4.64. 1.60. 168. 0.91. 72.8. 0.086. 0.34. 129.1. 1. 0. 1. *. ABELL 3562. 203.3825. -31.6731. 0.0484. 1025.3. 5.73. 1.71. 169. 0.84. 81. 0.000. 0.8. 78.4. 1. 0. 0. ABELL 3564. 203.5929. -35.2225. 0.0505. 380.9. 0.89. 0.92. 11. 0.58. 10.5. 0.873. 0.47. 49.3. 0. 0. 0. SC 336-314. 204.0792. -31.8000. 0.0395. 236.9. 0.22. 0.57. 6. 0.31. 4.9. 0.682. 0.88. 98.8. 0. 1. 0. ABELL 3566. 204.7475. -35.5536. 0.0514. 494.7. 1.94. 1.19. 35. 0.84. 39.7. 0.347. 0.6. 119.9. 1. 0. 1. ABELL 3568. 205.3459. -34.3878. 0.0528. 247.1. 0.24. 0.60. 4. 0.75. 6.8. -. 0.42. 165.6. 1. 0. 0. ABELL S0740. 205.8846. -38.1847. 0.0353. 588.6. 3.35. 1.43. 34. 0.84. 48. 0.005. 0.36. 64.0. 1. 0. 0. 3.3 Summary of Properties of Galaxy Clusters and Groups in the SSC. Table 3.2 – continued.. 33.

(56) 34. Table 3.2 – continued. Dec. (Deg). (Deg). ABELL S0742. 206.1479. -34.3008. *. ABELL 3570. 206.7113. *. ABELL 3571. *. z. Nv. f. N2mass× f. DS-test. e. PA. cBCG. cX. BCG. σv. M200. r200. (km s−1 ). (1014 M

(57) ). (Mpc). 0.0504. 126.6. 0.03. 0.31. 4. 0.57. 7.4. -. 0.56. 66.5. 0. 0. 0. -37.9161. 0.0376. 405.6. 2.71. 1.34. 32. 0.87. 47.7. 0.958. 0.54. 55.2. 1. 0. 0. 206.8704. -32.8658. 0.0390. 1057.3. 16.29. 2.43. 170. 0.91. 152.5. 0.641. 0.57. 14.6. 1. 1. 0. ABELL 3575. 208.1492. -32.8797. 0.0369. 267.9. 0.31. 0.65. 7. 0.67. 8. 0.433. 0.23. 122.4. 1. 0. 0. ABELL 3577. 208.3721. -27.8886. 0.0487. 559.9. 2.16. 1.24. 28. 0.69. 41.8. 0.73. 0.27. 112.6. 1. 0. 0. SSGC 006. 193.4121. -28.3119. 0.0547. 389.0. 0.94. 0.94. 13. 0.75. 6.8. 0.95. 0.07. 58.1. 1. 0. 0. AM 1259-322. 195.5417. -32.7681. 0.0312. 242.4. 0.23. 0.59. 6. 0.36. 5.1. 0.666. 0.68. 16.3. 0. 0. 0. SSGC 036. 196.1788. -32.2089. 0.0316. 130.5. 0.04. 0.32. 5. 0.71. 7.1. 0.12. 0.44. 27.9. 0. 0. 0. SSGC 038. 196.4650. -31.4969. 0.0539. 145.2. 0.05. 0.35. 4. 1. 4. -. 0.08. 9.9. 0. 0. 0. SSGC 041. 196.5408. -29.1450. 0.0498. 144.5. 0.05. 0.35. 4. 0.8. 5.6. -. 0.02. 134.1. 0. 0. 0. SSGC 043. 196.8541. -31.7190. 0.0519. 302.0. 0.44. 0.73. 3. 1. 7. -. 0.62. 127.2. 0. 0. 1. SSGC 058. 200.2029. -35.1231. 0.0507. 333.1. 0.59. 0.80. 4. 0.67. 6.7. -. 0.64. 25.4. 0. 0. 0. SSGC 059. 200.2988. -31.1081. 0.0478. 409.8. 1.11. 0.99. 4. 0.5. 5.5. -. 0.13. 178.3. 0. 0. 0. SSGC 060. 200.4658. -30.1650. 0.0473. 326.4. 0.56. 0.79. 3. 1. 6. -. 0.25. 55.8. 0. 0. 0. AM 1320-330. 200.7042. -33.4161. 0.0484. 101.8. 0.02. 0.25. 4. 0.8. 4. -. 0.54. 46.6. 0. 0. 0. SSGC 072. 201.5629. -28.8269. 0.0469. 147.7. 0.05. 0.36. 3. 0.67. 3.3. -. 0.21. 136.9. 0. 0. 0. prob.. (Deg). AGN. Chapter 3 Properties of Galaxy Clusters and Groups in the SSC. RA. name.

(58) RA. Dec. (Deg). (Deg). SSGC 075. 201.9187. -30.6350. SSGC 079. 202.0629. SSGC 077. name. z. Nv. f. N2mass× f. DS-test. e. PA. cBCG. cX. BCG. σv. M200. r200. (km s−1 ). (1014 M

(59) ). (Mpc). 0.0478. 367.8. 0.80. 0.89. 6. 0.83. 6.7. 0.702. 0.44. 90.1. 0. 0. 0. -34.0061. 0.0492. 357.7. 0.74. 0.86. 5. 0.71. 14.3. 0.658. 0.63. 150.6. 0. 0. 0. 202.1871. -27.9289. 0.0335. 416.8. 1.19. 1.01. 26. 0.68. 31.1. 0.391. 0.44. 121.3. 0. 0. 0. SSGC 087. 202.7258. -30.4961. 0.0497. 301.8. 0.44. 0.73. 8. 0.78. 8.6. 0.014. 0.42. 45.2. 0. 0. 0. SSGC 097. 205.1779. -34.0519. 0.0502. 390.7. 0.96. 0.94. 12. 1. 14. 0.204. 0.61. 111.4. 0. 0. 0. SSC01. 192.7728. -22.5631. 0.0447. 413.8. 1.15. 1.00. 7. 1. 27. 0.745. 0.23. 95.0. 1. 0. 0. SSC02. 193.7062. -26.7706. 0.0592. 336.7. 0.60. 0.81. 18. 0.75. 13.5. 0.284. 0.53. 0.2. 1. 0. 1. SSC03. 195.3994. -23.9902. 0.0457. 287.0. 0.38. 0.69. 14. 0.71. 7.9. 0.717. 0.08. 74.5. 1. 0. 1. SSC04. 198.5288. -33.8171. 0.0504. 376.0. 0.85. 0.91. 10. 1. 18. 0.396. 0.63. 46.3. 0. 0. 0. SSC05. 198.7860. -37.1698. 0.0361. 324.9. 0.56. 0.79. 10. 0.77. 13.8. 0.605. 0.49. 120.0. 0. 0. 0. SSC06. 198.9018. -32.7206. 0.0486. 342.7. 0.65. 0.83. 10. 0.75. 17.3. 0.92. 0.76. 139.2. 0. 0. 0. SSC07. 199.9164. -26.4250. 0.0455. 170.1. 0.08. 0.41. 4. 1. 4. -. 0.08. 1.8. 1. 0. 1. SSC08. 199.9185. -23.7750. 0.0459. 288.2. 0.39. 0.70. 5. 0.83. 9.2. 0.623. 0.49. 26.9. 0. 0. 0. SSC09. 200.9993. -34.6214. 0.0496. 361.0. 0.76. 0.87. 9. 0.8. 12.8. 0.307. 0.4. 5.5. 0. 0. 0. SSC10. 201.4447. -32.0673. 0.0473. 380.0. 0.88. 0.92. 21. 0.86. 14.6. 0.048. 0.36. 52.3. 0. 0. 0. SSC11. 201.7257. -24.6631. 0.0456. 459.0. 1.56. 1.11. 21. 0.74. 21.4. 0.817. 0.79. 134.2. 0. 0. 0. prob.. (Deg). AGN. 3.3 Summary of Properties of Galaxy Clusters and Groups in the SSC. Table 3.2 – continued.. 35.

(60) 36. Table 3.2 – continued. Dec. (Deg). (Deg). SSC12. 201.8486. -25.4115. SSC13. 202.5877. SSC14. z. Nv. f. N2mass× f. DS-test. e. PA. cBCG. cX. BCG. σv. M200. r200. (km s−1 ). (1014 M

(61) ). (Mpc). 0.0440. 326.7. 0.56. 0.79. 9. 0.8. 11.2. 0.857. 0.19. 30.6. 1. 0. 0. -30.6999. 0.0502. 343.0. 0.65. 0.83. 8. 0.67. 9.3. 0.003. 0.81. 137.8. 0. 0. 0. 203.0635. -31.0399. 0.0449. 262.9. 0.29. 0.64. 7. 0.83. 5.8. 0.95. 0.35. 130.4. 0. 0. 0. SSC15. 203.1691. -23.4846. 0.0334. 158.0. 0.06. 0.38. 5. 0.63. 7.5. 0.131. 0.07. 118.1. 0. 0. 0. SSC16. 206.8386. -37.4117. 0.0386. 389.5. 0.96. 0.95. 8. 0.89. 14.2. 0.424. 0.94. 7.2. 0. 0. 0. SSC17. 209.2576. -24.8351. 0.0376. 375.0. 0.86. 0.91. 10. 0.5. 11. 0.046. 0.69. 50.1. 0. 0. 0. prob.. (Deg). AGN. Column (1): “*” : X-ray detection by REFLEX (Böhringer et al. 2004); “+”: X-ray detection by de Filippis et al. (2005). Column(2): cluster/group name. Column (3)(4): RA, Dec (J2000.0). Column (5): redshift. Column (6): σv : velocity dispersion. Column (7): M200 . Column (8): r200 . Column (9): Nv : number of cluster members with measured velocity. Column (10): f : fraction of galaxies within r200 that have velocities within 3σv . Column (11): N2mass× f : number of cluster members estimated from 2MASS. Column (12): probability of DS-test, those with Nv < 5 are denoted by “-”. Column (13): e: cluster ellipticity. Column (14): “PA”: position angel of cluster major axis, measured from the north increasing towards the east. Column (15): cBCG : cluster center defined by early type BCG: 0: no, 1: yes. Column (16): cX : cluster center defined by the peak of X-ray emission: 0: no, 1: yes. Column (17): BCG is detected by NVSS 1.4 GHz as an AGN, 0: no, 1: yes.. Chapter 3 Properties of Galaxy Clusters and Groups in the SSC. RA. name.