Weak‐Lensing Mass Distributions for 24 X‐Ray Abell Clusters

Abstract

We use the weak gravitational lensing effect to study the mass distribution and dynamical state of a sample of 24 X-ray luminous clusters of galaxies (0.05 < z < 0.31) observed with the FORS1 instrument mounted on the VLT-Antu (Unit Telescope 1) under homogeneous sky conditions and subarsecond image quality. The galaxy shapes were measured in the combined V, I, R image after deconvolution with a locally determined point-spread-function, while the two-dimensional mass distributions of the clusters were computed using an algorithm based on the maximum entropy method. By comparing the mass and light distributions of the clusters in our sample, we find that their mass centers, for the majority of the clusters, is consistent with the positions of optical centers. We find that some clusters present significant mass substructures which generally have optical counterparts. At least in one cluster (Abell 1451), we detect a mass substructure without an obvious luminous counterpart. The radial profile of the shear of the clusters was fitted using circular and elliptical isothermal elliptical distributions, which allowed the finding of a strong correlation between the orientation of the major-axis of the matter distribution and the corresponding major-axes of the brightest cluster galaxy light-profiles. Estimates of how close to dynamical relaxation are these clusters were obtained through comparison of our weaklensing mass measurements with the x-ray and velocity dispersion determinations available in the literature. We find that clusters with intra-cluster gas colder than 8 keV show a good agreement between the different mass determinations, but clusters with gas hotter than 8 keV present discrepant mass values. The clusters diagnosed to be out of equilibrium are Abell 1451, 2163 and 2744, all of them having hints of substructure. Abell 2744 presents the largest discrepancy between its X-ray and weak-lensing temperature determinations, which can be interpreted as being due to the interaction between the two kinematical components along the line of sight found by Girardi & Mezzeti (2001).

RELICS: Strong Lens Models for Five Galaxy Clusters from the Reionization Lensing Cluster Survey

“…Several weak lensing models have been published for this cluster (Squires et al 1997;Cypriano et al 2004;Radovich et al 2008;Okabe et al 2011;Soucail 2012). The most direct link we can make between our strong lensing model and these weak lensing models comes from a comparison of the mass measured by weak lensing in the area covered by our model.…”

The dark matter distribution inz ~ 0.5 clusters of galaxies

“…To correct for the PSF smearing, we use the Im2shape software (Bridle et al 2002), which has already demonstrated its potential to recover the intrinsic shape of the galaxies (Cypriano et al 2004;Bardeau et al 2005Bardeau et al , 2007Limousin et al 2007a,b). Starting with a given model for the shape of each object, the code convolves it with the local estimate of the PSF.…”

“…It also avoids the noise induced by galaxies whose shape is badly estimated because they are too close to bright cluster galaxies (e.g. Cypriano et al 2004).…”

“…3), the objects above this threshold being most likely false detections or very faint/small galaxies. Also thanks to our weighting scheme, removing them does not have any consequences on the final mass estimates (see Cypriano et al 2004, for details).…”

“…To get a reliable faint-galaxy redshift distribution, we used the photometric redshifts of galaxies in reference fields, neglecting the cosmic variance between different fields (Cypriano et al 2004;Hoekstra 2007;Limousin et al 2009;Oguri et al 2009). Observations in the CFHTLS Deep fields obtained with the same instrument form the ideal data set for our study (Gavazzi & Soucail 2007).…”