The complex galaxy cluster Abell 514: New results obtained with the XMM - Newton satellite

We study the X-ray morphology and dynamics of the galaxy cluster Abell 514. Also, the relation between the X-ray properties and Faraday Rotation measures of this cluster are investigated in order to study the connection of magnetic fields and the intra-cluster medium. We use two combined XMM - Newton pointings that are split into three distinct observations. The data allow us to evaluate the overall cluster properties like temperature and metallicity with high accuracy. Additionally, a temperature map and the metallicity distribution are computed, which are used to study the dynamical state of the cluster in detail. Abell 514 represents an interesting merger cluster with many substructures visible in the X-ray image and in the temperature and abundance distributions. The new XMM - Newton data of Abell 514 confirm the relation between the X-ray brightness and the sigma of the Rotation Measure (S_X - sigma_RM relation) proposed by Dolag et al. (2001).Comment: 9 pages, 13 figures, accepted for publication in A&

X-ray measured metallicities of the intra-cluster medium: a good measure for the metal mass?

Aims. We investigate whether X-ray observations map heavy elements in the Intra-Cluster Medium (ICM) well and whether the X-ray observations yield good estimates for the metal mass, with respect to predictions on transport mech- anisms of heavy elements from galaxies into the ICM. We further test the accuracy of simulated metallicity maps. Methods. We extract synthetic X-ray spectra from N-body/hydrodynamic simulations including metal enrichment pro- cesses, which we then analyse with the same methods as are applied to observations. By changing the metal distribution in the simulated galaxy clusters, we investigate the dependence of the overall metallicity as a function of the metal distribution. In addition we investigate the difference of X-ray weighted metal maps produced by simulations and metal maps extracted from artifcial X-ray spectra, which we calculate with SPEX2.0 and analyse with XSPEC12.0. Results. The overall metallicity depends strongly on the distribution of metals within the galaxy cluster. The more inhomogeneously the metals are distributed within the cluster, the less accurate is the metallicity as a measure for the true metal mass. The true metal mass is generally underestimated by X-ray observations. The difference between the X-ray weighted metal maps and the metal maps from synthetic X-ray spectra is on average less than 7% in the temperature regime above T > 3E7 K, i.e. X-ray weighted metal maps can be well used for comparison with observed metal maps. Extracting the metal mass in the central parts (r < 500 kpc) of galaxy clusters with X-ray observations results in metal mass underestimates up to a factor of three.Comment: 7 pages, 9 figures, accepted for publication in A&

Metal enrichment of the intra-cluster medium over a Hubble time for merging and relaxed galaxy clusters

We investigate the efficiency of galactic mass loss, triggered by ram-pressure stripping and galactic winds of cluster galaxies, on the chemical enrichment of the intra-cluster medium (ICM). We combine N-body and hydrodynamic simulations with a semi-numerical galaxy formation model. By including simultaneously different enrichment processes, namely ram-pressure stripping and galactic winds, in galaxy-cluster simulations, we are able to reproduce the observed metal distribution in the ICM. We find that the mass loss by galactic winds in the redshift regime z>2 is ~10% to 20% of the total galactic wind mass loss, whereas the mass loss by ram-pressure stripping in the same epoch is up to 5% of the total ram-pressure stripping mass loss over the whole simulation time. In the cluster formation epochs z<2 ram-pressure stripping becomes more dominant than galactic winds. We discuss the non-correlation between the evolution of the mean metallicity of galaxy clusters and the galactic mass losses. For comparison with observations we present two dimensional maps of the ICM quantities and radial metallicity profiles. The shape of the observed profiles is well reproduced by the simulations in the case of merging systems. In the case of cool-core clusters the slope of the observed profiles are reproduced by the simulation at radii below ~300 kpc, whereas at larger radii the observed profiles are shallower. We confirm the inhomogeneous metal distribution in the ICM found in observations. To study the robustness of our results, we investigate two different descriptions for the enrichment process interaction.Comment: 11 pages, 13 figures, accepted for publication in A&A, high resolution version can be found at <http://astro.uibk.ac.at/~wolfgang/kapferer.pdf

Intracluster medium of the merging cluster Abell 3395

We present a detailed imaging and spectral analysis of the merging environment of the bimodal cluster A3395 using X-ray and radio observations. X-ray images of the cluster show five main constituents of diffuse emission : A3395 NE, A3395 SW, A3395 NW, A3395 W, and a filament connecting NE to W. X-ray surface-brightness profiles of the cluster did not show any shock fronts in the cluster. Temperature and entropy maps show high temperature and high entropy regions in the W, the NW, the filament and between the NE and SW subclusters. The NE, SW and W components have X-ray bolometric luminosities similar to those of rich clusters of galaxies but have relatively higher temperatures. Similarly, the NW component has X-ray bolometric luminosity similar to that of isolated groups but with much higher temperature. It is, therefore, possible that all the components of the cluster have been heated by the ongoing mergers. The NE subcluster is the most massive and luminous constituent and other subclusters are found to be gravitationally bound to it. The W component is most probably either a clump of gas stripped off the SW due to ram pressure or a separate subcluster that has merged or is merging with the SW. No X-ray cavities are seen associated with the Wide Angle Tailed (WAT) radio source near the centre of the SW subcluster. Minimum energy pressure in the radio emission-peaks of the WAT galaxy is comparable with the external thermal pressure. The radio spectrum of the WAT suggests a spectral age of ~10Myr

Metal enrichment of the intra-cluster medium over a Hubble time for merging and relaxed galaxy clusters

We investigate the efficiency of galactic mass loss, triggered by ram-pressure stripping and galactic winds of cluster galaxies, on the chemical enrichment of the intra-cluster medium (ICM). We combine N-body and hydrodynamic simulations with a semi-numerical galaxy formation model. By including simultaneously different enrichment processes, namely ram-pressure stripping and galactic winds, in galaxy-cluster simulations, we are able to reproduce the observed metal distribution in the ICM. We find that the mass loss by galactic winds in the redshift regime z>2 is ~10% to 20% of the total galactic wind mass loss, whereas the mass loss by ram-pressure stripping in the same epoch is up to 5% of the total ram-pressure stripping mass loss over the whole simulation time. In the cluster formation epochs z<2 ram-pressure stripping becomes more dominant than galactic winds. We discuss the non-correlation between the evolution of the mean metallicity of galaxy clusters and the galactic mass losses. For comparison with observations we present two dimensional maps of the ICM quantities and radial metallicity profiles. The shape of the observed profiles is well reproduced by the simulations in the case of merging systems. In the case of cool-core clusters the slope of the observed profiles are reproduced by the simulation at radii below ~300 kpc, whereas at larger radii the observed profiles are shallower. We confirm the inhomogeneous metal distribution in the ICM found in observations. To study the robustness of our results, we investigate two different descriptions for the enrichment process interaction.Comment: 11 pages, 13 figures, accepted for publication in A&A, high resolution version can be found at <http://astro.uibk.ac.at/~wolfgang/kapferer.pdf

Rotation Measures of Radio Sources in Hot Galaxy Clusters

The goal of this work is to investigate the Faraday rotation measure (RM) of radio galaxies in hot galaxy clusters in order to establish a possible connection between the magnetic field strength and the gas temperature of the intracluster medium. We performed Very Large Array observations at 3.6 cm and 6 cm of two radio galaxies located in A401 and Ophiuchus, a radio galaxy in A2142, and a radio galaxy located in the background of A2065. All these galaxy clusters are characterized by high temperatures. We obtained detailed RM images at an angular resolution of 3'' for most of the observed radio galaxies. The RM images are patchy and reveal fine substructures of a few kpc in size. Under the assumption that the radio galaxies themselves have no effect on the measured RMs, these structures indicate that the intracluster magnetic fields fluctuate down to such small scales. These new data are compared with RM information present in the literature for cooler galaxy clusters. For a fixed projected distance from the cluster center, clusters with higher temperature show a higher dispersion of the RM distributions (sigmaRM), mostly because of the higher gas density in these clusters. Although the previously known relation between the clusters X-ray surface brightness (Sx) at the radio galaxy location and sigmaRM is confirmed, a possible connection between the sigmaRM-Sx relation and the cluster temperature, if present, is very weak. Therefore, in view of the current data, it is impossible to establish a strict link between the magnetic field strength and the gas temperature of the intracluster medium.Comment: Accepted by Astronomy and Astrophysics, 26 pages, 19 figure