We present the results of the dynamical analysis of the rich , hot , and X–ray very luminous galaxy cluster A2219 , containing a powerful diffuse radio–halo .
Our analysis is based on new redshift data for 27 galaxies in the cluster region , measured from spectra obtained at the TNG , with the addition of other 105 galaxies recovered from reduction of CFHT archive data in a cluster region of \sim 5 \arcmin radius ( \sim 0.8 h ^ { -1 } Mpc at the cluster distance ) centered on the cD galaxy .
The investigation of the dynamical status is also performed by using X–ray data stored in the Chandra archive .
Further , valuable information comes from other bands – optical photometric , infrared , and radio data – which are analyzed and/or discussed , too .
We find that A2219 appears as a peak in the velocity space at z = 0.225 , and select 113 cluster members .
We compute a high value for the line–of–sight velocity dispersion , \sigma _ { v } = 1438 ^ { +109 } _ { -86 } km s ^ { -1 } , consistent with the high average X–ray temperature of 10.3 keV .
If dynamical equilibrium is assumed , the virial theorem leads to M \sim 2.8 \times 10 ^ { 15 } h ^ { -1 } M _ { \odot } for the global mass within the virial region .
However , further investigation based on both optical and X–ray data shows significant signs of a young dynamical status .
In fact , we find strong evidence for the elongation of the cluster in the SE–NW direction coupled with a significant velocity gradient , as well as for the presence of substructure both in optical data and X–ray data .
Moreover , we point out the presence of several active galaxies .
We discuss the results of our multi–wavelength investigation suggesting a complex merging scenario where the main , original structure is subject to an ongoing merger with few clumps aligned in a filament in the foreground oriented along an oblique direction with respect to the line–of–sight .
Our conclusion supports the view of the connection between extended radio emission and merging phenomena in galaxy clusters .