A. Biviano

Velocity Dispersions and X-Ray Temperatures of Galaxy Clusters

Using a large and well-controlled sample of clusters of galaxies, we investigate the relation between cluster velocity dispersions and X-ray temperatures of intra-cluster gas. In order to obtain a reliable estimate of the total velocity dispersion of a cluster, independent of the level of anisotropies in galaxy orbits, we analyze the integrated velocity dispersion profiles over increasing distances from the cluster centers. Distortions in the velocity fields, the effect of close clusters, the presence of substructures, and the presence of a population of (spiral) galaxies not in virial equilibrium with the cluster potential are taken into account. Using our final sample of 37 clusters, for which a reliable estimate of the velocity dispersion could be obtained, we derive a relation between the velocity dispersions and the X-ray temperatures, with a scatter reduced by more than 30 % with respect to previous works. A chi square fit to the temperature-velocity dispersion relation does not exclude the hypothesis that the ratio between galaxy and gas energy density (the so-called spectral beta) is a constant for all clusters. In particular, the value of beta=1, corresponding to energy equipartition, is acceptable.

CLASH: Weak-lensing Shear-and-magnification Analysis of 20 Galaxy Clusters

We present a joint shear-and-magnification weak-lensing analysis of a sample of 16 X-ray-regular and 4 high-magnification galaxy clusters at 0.19 ≾ z ≾ 0.69 selected from the Cluster Lensing And Supernova survey with Hubble (CLASH). Our analysis uses wide-field multi-color imaging, taken primarily with Suprime-Cam on the Subaru Telescope. From a stacked-shear-only analysis of the X-ray-selected subsample, we detect the ensemble-averaged lensing signal with a total signal-to-noise ratio of ≃ 25 in the radial range of 200-3500 kpc h^(–1), providing integrated constraints on the halo profile shape and concentration-mass relation. The stacked tangential-shear signal is well described by a family of standard density profiles predicted for dark-matter-dominated halos in gravitational equilibrium, namely, the Navarro-Frenk-White (NFW), truncated variants of NFW, and Einasto models. For the NFW model, we measure a mean concentration of c_(200c)=4.01^(+0.35)_(-0.32) at an effective halo mass of M_(200c)=1.34^(+0.10)_(-0.09) x 10^(15)M_☉. We show that this is in excellent agreement with Λ cold dark matter (ΛCDM) predictions when the CLASH X-ray selection function and projection effects are taken into account. The best-fit Einasto shape parameter is ɑ_E=0.191^(+0.071)_(-0.068), which is consistent with the NFW-equivalent Einasto parameter of ~0.18. We reconstruct projected mass density profiles of all CLASH clusters from a joint likelihood analysis of shear-and-magnification data and measure cluster masses at several characteristic radii assuming an NFW density profile. We also derive an ensemble-averaged total projected mass profile of the X-ray-selected subsample by stacking their individual mass profiles. The stacked total mass profile, constrained by the shear+magnification data, is shown to be consistent with our shear-based halo-model predictions, including the effects of surrounding large-scale structure as a two-halo term, establishing further consistency in the context of the ΛCDM model.

The ESO Nearby Abell Cluster Survey.* XII. The Mass and Mass-to-Light Ratio Profiles of Rich Clusters

We determine the mass profile of an ensemble cluster built from 3056 galaxies in 59 nearby clusters observed in the ESO Nearby Abell Cluster Survey. The mass profile is derived from the distribution and kinematics of the early-type (elliptical and S0) galaxies only, with projected distances from the centers of their clusters ?1.5r200. These galaxies are most likely to meet the conditions for the application of the Jeans equation, since they are the oldest cluster population and are thus quite likely to be in dynamical equilibrium with the cluster potential. In addition, the assumption that the early-type galaxies have isotropic orbits is supported by the shape of their velocity distribution. For galaxies of other types (the brightest elliptical galaxies, with MR ? -22 + 5 log h, and the early and late spirals) these assumptions are much less likely to be satisfied. For the determination of the mass profile we also exclude early-type galaxies in subclusters. Application of the Jeans equation yields a nonparametric estimate of the cumulative mass profile M(<r), which has a logarithmic slope of -2.4 ? 0.4 in the density profile at r200 (approximately the virial radius). We compare our result with several analytical models from the literature and estimate their best-fit parameters from a comparison of observed and predicted velocity-dispersion profiles. We obtain acceptable solutions for all models (NFW, Moore et al., softened isothermal sphere [SIS], and Burkert). Our data do not provide compelling evidence for the existence of a core; as a matter of fact, the best-fitting core models have core-radii well below 100 h-1 kpc. The upper limit that we put on the size of the core-radius provides a constraint for the scattering cross section of dark matter particles. The total-mass density appears to be traced remarkably well by the luminosity density of the early-type galaxies. On the contrary, the luminosity density of the brightest elliptical galaxies increases faster toward the center than the mass density, while the luminosity density profiles of the early and late spirals are somewhat flatter than the mass density profile.

Velocity dispersions in galaxy clusters

We analyze the velocity dispersions of 79 galaxy clusters having at least 30 galaxies with available redshifts. We show that different estimates of velocity dispersion give similar results on cluster samples of at least ∼20 galaxies each. However, only robust estimates of velocity dispersion seem to be efficient on cluster samples with ∼10 galaxies each. A significant correlation is found to exist between the velocity dispersion and the cluster richness. We provide the distribution function of cluster velocity dispersions, normalized to the complete sample by Abell, Corwin, & Olowin (1989). Available theoretical models are compared with this distribution function

CLASH: The CONCENTRATION-MASS RELATION of GALAXY CLUSTERS

We present a new determination of the concentration–mass (c–M) relation for galaxy clusters based on our comprehensive lensing analysis of 19 X-ray selected galaxy clusters from the Cluster Lensing and Supernova Survey with Hubble (CLASH). Our sample spans a redshift range between 0.19 and 0.89. We combine weak-lensing constraints from the Hubble Space Telescope (HST) and from ground-based wide-field data with strong lensing constraints from HST. The results are reconstructions of the surface-mass density for all CLASH clusters on multi-scale grids. Our derivation of Navarro–Frenk–White parameters yields virial masses between 0.53 × 10^(15) M_⊙ h and 1.76 × 10^(15) M_⊙ h and the halo concentrations are distributed around c_(200c) ∼ 3.7 with a 1σ significant negative slope with cluster mass. We find an excellent 4% agreement in the median ratio of our measured concentrations for each cluster and the respective expectation from numerical simulations after accounting for the CLASH selection function based on X-ray morphology. The simulations are analyzed in two dimensions to account for possible biases in the lensing reconstructions due to projection effects. The theoretical c–M relation from our X-ray selected set of simulated clusters and the c–M relation derived directly from the CLASH data agree at the 90% confidence level.

An ISOCAM survey through gravitationally lensing galaxy clusters - I. Source lists and source counts for A370, A2218 and A2390

PCT No. PCT/DE89/00650 Sec. 371 Date Mar. 6, 1991 Sec. 102(e) Date Mar. 6, 1991 PCT Filed Oct. 12, 1989 PCT Pub. No. WO90/04702 PCT Pub. Date May 3, 1990.A partial flue gas stream is used for the production of electrical energy and/or heating and operational heat by utilizing combustion heat from fossil fuels, prior to combustion dried in an indirectly heated fluidized bed dryer, with combustion flue gas used as a carrier medium for the fluidized bed dryer. The mixture of flue gases and steam, deriving from the drying process, is after an intermediate treatment, if necessary, discharged with the main flue gas stream.

The Mass Profile of Galaxy Clusters out to ~2r200

We use the public release of 100,000 galaxies from the Two Degree Field Galaxy Redshift Survey (2dFGRS) to analyze the internal dynamics of galaxy clusters. We select 43 noninteracting clusters that are adequately sampled in the 2dFGRS public release. Members of these clusters are selected out to ~2 virial radii. We build an ensemble cluster by stacking together the 43 clusters, after appropriate scaling of their galaxy velocities and clustercentric distances. We solve the Jeans equation for the hydrostatic equilibrium for the member galaxies within the virial radius of the ensemble cluster, assuming isotropic orbits. We constrain the cluster mass profile within the virial radius by exploring parameterized models for the cluster mass density profile. We find that both cuspy profiles and profiles with a core are acceptable. In particular, the concentration parameter of the best-fit Navarro-Frenk-White model is as predicted from numerical simulations in a Λ cold dark matter cosmology. Density profiles with very large core radii are ruled out. Beyond the virial radius, dynamical equilibrium cannot be taken for granted, and the Jeans equation may not be applicable. In order to extend our dynamical analysis out to ~2 virial radii, we rely on the method that uses the amplitude of the caustics in the space of galaxy clustercentric distances and velocities. We find very good agreement between the mass profile determined with the caustic method and the extrapolation to ~2 virial radii of the best-fit mass profile determined by the Jeans analysis in the virialized inner region. We determine the mass-to-number density profile and find that it is fully consistent with a constant within the virial radius. The mass-to-number density profile is, however, inconsistent with a constant when the full radial range from 0 to ~2 virial radii is considered, unless the sample used to determine the number density profile is restricted to the early-type galaxies.

Hubble Space Telescope Combined Strong and Weak Lensing Analysis of the CLASH Sample: Mass and Magnification Models and Systematic Uncertainties

We present results from a comprehensive lensing analysis in HST data, of the complete CLASH cluster sample. We identify new multiple-images previously undiscovered allowing improved or first constraints on the cluster inner mass distributions and profiles. We combine these strong-lensing constraints with weak-lensing shape measurements within the HST FOV to jointly constrain the mass distributions. The analysis is performed in two different common parameterizations (one adopts light-traces-mass for both galaxies and dark matter while the other adopts an analytical, elliptical NFW form for the dark matter), to provide a better assessment of the underlying systematics - which is most important for deep, cluster-lensing surveys, especially when studying magnified high-redshift objects. We find that the typical (median), relative systematic differences throughout the central FOV are

RASS-SDSS galaxy cluster survey III. Scaling relations of galaxy clusters

\sim40\%

The relation between velocity dispersion and mass in simulated clusters of galaxies: dependence on the tracer and the baryonic physics

in the (dimensionless) mass density,