2005ApJ...619L.143B

Subaru observations of A1689 (z=0.183) are used to derive an accurate, model-independent mass profile for the entire cluster, r≲2 Mpc h^–1, by combining magnification bias and distortion measurements. The projected mass profile steepens quickly with increasing radius, falling away to zero at r∼1.0 Mpc h^–1, well short of the anticipated virial radius. Our profile accurately matches the inner profile, r≲200 kpc h^–1, derived from deep Hubble Space Telescope Advanced Camera for Surveys (ACS) images. The combined ACS and Subaru information is well fitted by a Navarro-Frenk-White profile with virial mass, (1.93±0.20)x10¹⁵ M_☉, and surprisingly high concentration, c_vir=13.7^+1.4_–1.1, significantly larger than theoretically expected (c_vir≃4), corresponding to a relatively steep overall profile. A slightly better fit is achieved with a steep power-law model, dlogΣ(θ)/dlogθ≃-3, with a core θ_c≃1'.7 (r_c≃210 kpc h^–1), whereas an isothermal profile is strongly rejected. These results are based on a reliable sample of background galaxies selected to be redder than the cluster E/S0 sequence. By including the faint blue galaxy population, a much smaller distortion signal is found, demonstrating that blue cluster members significantly dilute the true signal for r≲400 kpc h^–1. This contamination is likely to affect most weak lensing results to date.