A weak-gravitational lensing analysis of massive galaxy clusters at 0.3 Z 0.7.

摘要

A weak-gravitational lensing analysis of 34 massive galaxy clusters from the MAssive Cluster Survey (MACS) is presented. These clusters, in the redshift range 0.35 ≤ z ≤ 0.7, have X-ray luminosities greater than 6 x 1044 erg s-1. The clusters were observed with SuprimeCam on the 8.3 m Subaru Telescope. This instrument is well-suited for weak-lensing studies because of its wide field of view and large light gathering power. A parallel-computing data processing pipeline has been developed for the analysis of this data. A non-parametric weak-lensing reconstruction algorithm was used to produce maps of the spatial distribution of mass for the 34 clusters. In addition, the total mass of 31 of these clusters have been estimated using a fit to a NFW universal density profile. Fits to the data for 21 clusters have been found to be statistically acceptable (i.e., probability of exceeding chi2 greater than 13%). Systematics of weak-gravitational lensing data have been investigated, including the effect of galaxy selection criteria on the total mass estimate derived from weak-lensing analysis. Because of V - I color degeneracy, the technique of eliminating cluster members by color selection used at z ≲ 0.2 does not apply at higher redshift ranges, especially for z ≥ 0.5. In addition, a comparison between the mass estimates derived from weak-lensing and those derived from X-ray measurements for 11 of the relaxed clusters in the sample finds that the average mass ratio determined from weak-lensing is 2 +/- 9% lower than those determined by X-rays for this sample. While the average offset between masses estimated from weak-lensing and X-rays is smaller than previously reported by other authors, a few clusters had weak-lensing masses that were lower than the X-rays by a factor two. Possible explanations for this discrepancy are presented, such as overestimation of the X-ray masses because of cluster elongation along the line of sight or underestimation of the weak-lensing masses because of shear dilution by cluster members. Further investigation of these effects using photometric redshift data is suggested to understand these discrepancies.