Gemini and Chandra Observations of Abell 586, A Relaxed Strong-lensing Cluster

We analyze the mass content of the massive strong-lensing cluster Abell 586 (z = 0.17). We use optical data (imaging and spectroscopy) obtained with the Gemini Multi-Object Spectrograph (GMOS) mounted on the 8 m Gemini North telescope, together with publicly available X-ray data taken with the Chandra space telescope. Employing different techniques—velocity distribution of galaxies, weak gravitational lensing, and spatially resolved X-ray spectroscopy—we derive mass and velocity dispersion estimates from each of them. All estimates agree well with each other, within a 68% confidence level, indicating a velocity dispersion of 1000-1250 km s-1. The projected mass distributions obtained through weak lensing and X-ray emission are strikingly similar, having nearly circular geometry. We suggest that Abell 586 is probably a truly relaxed cluster whose last major merger occurred more than ~4 Gyr ago.