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Date and Time of the Query: 2019-04-25 T01:42:35 PDT
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For refcode 2008A&A...481..593M:
Retrieve 513 NED objects in this reference.
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Copyright by European Southern Observatory (ESO). Reproduced by permission
2008A&A...481..593M A 2163: Merger events in the hottest Abell galaxy cluster. I. Dynamical analysis from optical data Maurogordato, S.; Cappi, A.; Ferrari, C.; Benoist, C.; Mars, G.; Soucail, G.; Arnaud, M.; Pratt, G. W.; Bourdin, H.; Sauvageot, J.-L. Abstract. Context: A 2163 is among the richest and most distant Abell clusters, presenting outstanding properties in different wavelength domains. X-ray observations have revealed a distorted gas morphology and strong features have been detected in the temperature map, suggesting that merging processes are important in this cluster. However, the merging scenario is not yet well-defined. Aims: We have undertaken a complementary optical analysis, aiming to understand the dynamics of the system, to constrain the merging scenario and to test its effect on the properties of galaxies. Methods: We present a detailed optical analysis of A 2163 based on new multicolor wide-field imaging and medium-to-high resolution spectroscopy of several hundred galaxies. Results: The projected galaxy density distribution shows strong subclustering with two dominant structures: a main central component (A), and a northern component (B), visible both in optical and in X-ray, with two other substructures detected at high significance in the optical. At magnitudes fainter than R=19, the galaxy distribution shows a clear elongation approximately with the east-west axis extending over 4~h_70_^-1^ Mpc, while a nearly perpendicular bridge of galaxies along the north-south axis appears to connect (B) to (A). The (A) component shows a bimodal morphology, and the positions of its two density peaks depend on galaxy luminosity: at magnitudes fainter than R = 19, the axis joining the peaks shows a counterclockwise rotation (from NE/SW to E-W) centered on the position of the X-ray maximum. Our final spectroscopic catalog of 512 objects includes 476 new galaxy redshifts. We have identified 361 galaxies as cluster members; among them, 326 have high precision redshift measurements, which allow us to perform a detailed dynamical analysis of unprecedented accuracy. The cluster mean redshift and velocity dispersion are respectively z= 0.2005 +/- 0.0003 and 1434 +/- 60 km s^-1^. We spectroscopically confirm that the northern and western components (A 2163-B and A 2163-C) belong to the A 2163 complex. The velocity distribution shows multi-modality, with an overall bimodal structure peaking at ~59 200 km s^-1^ and ~60 500 km s^-1^. A significant velocity gradient (~1250 km s^-1^) is detected along the NE/SW axis of the cluster, which partially explains the detected bimodality. A 2163 appears to be exceptionally massive: the cluster virial mass is M_vir = 3.8 +/- 0.4 x 10^15^~M_o~h_70_^-1^. Conclusions: Our analysis of the optical data, combined with the available information from X-ray observations and predictions of numerical simulations, supports a scenario in which A 2163-A has undergone a recent (t ~ 0.5 Gyr) merger along a NE/SW (or E-W) axis, and A 2163-B is connected to the main complex, and is probably infalling on A 2163-A. Key words: galaxies: clusters: general, galaxies: kinematics and dynamics, galaxies clusters: individual: A 2163
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