MASS AND HOT BARYONS IN MASSIVE GALAXY CLUSTERS FROM SUBARU WEAK-LENSING AND AMiBA SUNYAEV-ZEL'DOVICH EFFECT OBSERVATIONS*

摘要

We present a multiwavelength analysis of a sample of four hot (TX 8 keV) X-ray galaxy clusters (A1689, A2261, A2142, and A2390) using joint AMiBA Sunyaev-Zel'dovich effect (SZE) and Subaru weak-lensing observations, combined with published X-ray temperatures, to examine the distribution of mass and the intracluster medium (ICM) in massive cluster environments. Our observations show that A2261 is very similar to A1689 in terms of lensing properties. Many tangential arcs are visible around A2261, with an effective Einstein radius ~40'' (at z ~ 1.5), which when combined with our weak-lensing measurements implies a mass profile well fitted by a Navarro-Frenk-White model with a high concentration c vir ~ 10, similar to A1689 and to other massive clusters. The cluster A2142 shows complex mass substructure, and displays a shallower profile (c vir ~ 5), consistent with detailed X-ray observations which imply recent interaction. The AMiBA map of A2142 exhibits an SZE feature associated with mass substructure lying ahead of the sharp northwest edge of the X-ray core suggesting a pressure increase in the ICM. For A2390 we obtain highly elliptical mass and ICM distributions at all radii, consistent with other X-ray and strong-lensing work. Our cluster gas fraction measurements, free from the hydrostatic equilibrium assumption, are overall in good agreement with published X-ray and SZE observations, with the sample-averaged gas fraction of f gas(r 200) = 0.133 ± 0.027, for our sample with M vir = (1.2 ± 0.1) × 1015 M ☉ h –1. When compared to the cosmic baryon fraction fb = Ω b /Ω m constrained by the WMAP five-year data, this indicates f gas,200/fb = 0.78 ± 0.16, i.e., (22 ± 16)% of the baryons are missing from the hot phase of clusters.