Combined strong and weak lensing analysis of 28 clusters from the Sloan Giant Arcs Survey★

Abstract

We study the mass distribution of a sample of 28 galaxy clusters using strong\nand weak lensing observations. The clusters are selected via their strong\nlensing properties as part of the Sloan Giant Arcs Survey (SGAS) from the Sloan\nDigital Sky Survey (SDSS). Mass modelling of the strong lensing information\nfrom the giant arcs is combined with weak lensing measurements from deep\nSubaru/Suprime-cam images to primarily obtain robust constraints on the\nconcentration parameter and the shape of the mass distribution. We find that\nthe concentration c_vir is a steep function of the mass, c_vir \\propto\nM_vir^-0.59\\pm0.12, with the value roughly consistent with the\nlensing-bias-corrected theoretical expectation for high mass (10^15 h^-1 M_sun)\nclusters. However, the observationally inferred concentration parameters appear\nto be much higher at lower masses (10^14 h^-1 M_sun), possibly a consequence of\nthe modification to the inner density profiles provided by baryon cooling. The\nsteep mass-concentration relation is also supported from direct stacking\nanalysis of the tangential shear profiles. In addition, we explore the\ntwo-dimensional shape of the projected mass distribution by stacking weak\nlensing shear maps of individual clusters with prior information on the\nposition angle from strong lens modelling, and find significant evidence for a\nlarge mean ellipticity with the best-fit value of e = 0.47 \\pm 0.06 for the\nmass distribution of the stacked sample. We find that the luminous cluster\nmember galaxy distribution traces the overall mass distribution very well,\nalthough the distribution of fainter cluster galaxies appears to be more\nextended than the total mass.\n