VIMOS-IFU survey of z ~ 0.2 massive galaxy clusters. I. Observations of the strong lensing cluster Abell 2667
Résumé
We present extensive multi-color imaging and low-resolution VIMOS integral field unit (IFU) spectroscopic observations of the X-ray luminous cluster Abell 2667 (z=0.233). An extremely bright giant gravitational arc (z=1.0334 ± 0.0003) is easily identified as part of a triple image system, and other fainter multiple images are also revealed by the Hubble Space Telescope Wide Field Planetary Camera-2 images. The VIMOS-IFU observations cover a field of view of 54'' × 54'' and enable us to determine the redshift of all galaxies down to V_606=22.5. Furthermore, redshifts could be identified for some sources down to V_606=23.2. In particular we identify 21 members in the cluster core, from which we derive a velocity dispersion of σ=960-120+190 km s-1, corresponding to a total mass of 7.1± 1.8 × 1013 h70-1 M_&sun; within a 110 h70-1 kpc (30 arcsec) radius. Using the multiple images constraints and priors on the mass distribution of cluster galaxy halos we construct a detailed lensing-mass model leading to a total mass of 2.9 ± 0.1 × 1013 h70-1 M_&sun; within the Einstein radius (16 arcsec). The lensing mass and dynamical mass are in good agreement, although the dynamical one is much less accurate. Within a 110 h70-1 kpc radius, we find a rest-frame K-band M/L ratio of 61± 5 h70 M_&sun;/L_&sun;. Comparing these measurements with published X-ray analysis is, however, less conclusive. Although the X-ray temperature matches the dynamical and lensing estimates, the published NFW mass model derived from the X-ray measurement with its low concentration of c ˜ 3 cannot account for the large Einstein radius observed in this cluster. A higher concentration of ˜ 6 would, however, match the strong lensing measurements. These results very likely reflect the complex structure of the cluster mass distribution, underlying the importance of panchromatic studies from small to large scale in order to better understand cluster physics.