Complex Structure of Galaxy Cluster A1689: Evidence for a Merger from X-Ray Data?

• Published in: The Astrophysical journal 2004-05, Vol.607 (1), p.190-201
• Main Authors: Andersson, K. E, Madejski, G. M
• Format: Article
• Language: English
• Subjects: dark matter; galaxies : clusters : individual (A1689); X-rays : galaxies : clusters
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.1086/383258

A1689 is a galaxy cluster at z = 0.183 for which previous measurements of its mass by using various techniques gave discrepant results. We present a new detailed measurement of the mass with the data based on X-ray observations with the European Photon Imaging Camera aboard the XMM-Newton Observatory, determined by using an unparameterized deprojection technique. Fitting the total mass profile to a Navarro-Frenk-White model yields halo concentration c = 7.2[image] and r sub(200) = 1.13 plus or minus 0.21 h super(-1) Mpc, corresponding to a mass that is less than half of that found from gravitational lensing. Adding to the evidence of substructure from optical observations, X-ray analysis shows a highly asymmetric temperature profile and a nonuniform redshift distribution, implying large-scale relative motion of the gas. A lower than expected gas mass fraction f sub(gas) = 0.072 plus or minus 0.008 (for a flat lambda CDM cosmology) suggests a complex spatial and/or dynamical structure. We also find no sign of any additional absorbing component previously reported on the basis of the Chandra data, confirming the XMM-Newton low-energy response by using data from ROSAT.