The Dynamical State of Massive Galaxy Clusters

1. σtotal = 1777 km/s • σA = 1121 km/s • σB = 682 km/s SingularIsothermal Sphere(SIS) Girardi & Mezzetti (2001) STARS GALAXIES • Clusters as cosmoligical probes ? • Depends strongly on a well calibrated and tight Mass × Observable relation • Widely available observables (V TX LXS-Z ) depend on the dynamical state of the cluster • Comparison with weak-lensing equivalents allows the diagnose whether the cluster is relaxed or not 10-15 gal. arcmin-2 1 Seeing ~ 0.6” Ellip. ~ 3% • Shear Radial Profile • To overcame the mass sheet degeneracy we estimate mass by fitting SIS profiles to the radial shear data thus obtaining SIS 4 • Sample & Observations • 24 Abell clusters (0.05<z<0.30) with Lx> 5  1044 erg s-1 (XBAC’s Ebeling 1996) • Imaging: V R I (330 s each) with FORS1@VLT (FoV: 6.8’6.8’) A1451 2 6 • “...establishing equilibrium after a merger event” (Valtachanov et al. 2002) A2163 7 • “State of violent activity” (Markevitch & Vickhlinin 2001) A2744 A2163 A1451 A1451 A2163 A2744 V~ SIS TX~ TSIS X-ray measured ICM temperature profile (left) and distribution (right) showing a complete lack of isothermality. A2744 (AC118) 8 • Particular case: Virial mass > Lensing > X-rays Interpretation: There are two structures along the line of sight The superposition of structures artificially increases V Lensing measures the mass of both structures TX measures, based on X-ray spectra will be dominated by the more luminous structure only. The Dynamical State of Massive Galaxy Clusters Eduardo S. Cypriano (UCL-UK), Laerte Sodré Jr. (USP-Brazil), Jean-Paul Kneib OAMP-France) & Luis Campusano (U. de Chile) Shape measurments 3 • Algorithm:Im2shape (Bridle et al. 1998) • Stars (PSF probes) selected by their FWHM • Shapes of galaxies are deconvolved by the local PSF Lensing × dynamical mass proxies 5 • The plots show the comparison between dynamical mass proxies: X-ray temperature and galaxy velocity dispersion, with its lensing counterparts • Most clusters seems to be in equilibrium (i.e. lensing and dynamical methods in agreement) but it is not true for the hottest (TX > 8keV) and with higher vel. disp. (V > 1100 km/s) ones. Detailed studies of the clusters with the highest lensing × dynamical discrepancy confirms that they are dynamically active • Conclusions • Lensing to dynamical mass discrepancy do seems to probe the dynamical state of galaxy clusters. • Most of the low-z X-ray luminous clusters of our sample are close to a state of dynamical equilibrium. • Dynamical activity appears to be more frequent for high mass clusters  Consistent with the hierarchical scenario. • Active (merging) clusters tend to have higher ICM temperatures than expected given their masses.