W. Domainko

Metal Enrichment Processes in the Intra-Cluster Medium

Institut fu¨r Astronomie, Universit¨at Wien, Tu¨rkenschanzstr. 17, 1180 Vienna, AustriaReceived / AcceptedAbstract. We present numerical simulations of galaxy clusters which include interaction processes between thegalaxies and the intra-cluster gas. The considered interaction processes are galactic winds and ram-pressurestripping, which both transfer metal-enriched interstellar medium into the intra-cluster gas and hence increase itsmetallicity. We investigate the efficiency and time evolution of the interaction processes by simulated metallicitymaps, which are directly comparable to those obtained from X-ray observations. We find that ram-pressurestripping is more efficient than quiet (i.e. non-starburst driven) galactic winds in the redshift interval between 1and 0. The expelled metals are not mixed immediately with the intra-cluster gas, but inhomogeneities are visiblein the metallicity maps. Even stripes of higher metallicity that a single galaxy has left behind can be seen. Thespatial distribution of the metals transported by ram-pressure stripping and by galactic winds are very differentfor massive clusters: the former process yields a centrally concentrated metal distribution while the latter resultsin an extended metal distribution.Key words. Galaxies:clusters:general – Galaxies:abundances – Galaxies:interactions – Galaxies:ISM – X-ray:galaxies:clusters

Discovery of diffuse radio emission at the center of the most X-ray-luminous cluster RX J1347.5-1145

Context. We report on new VLA radio observations of the distant cluster RX J1347.5-1145, which is the most luminous in X-rays. Aims. We aim at investigating the possible presence of diffuse and extended radio emission in this very peculiar system which shows both a massive cooling flow and merging signatures. Methods. New low resolution (∼18 arcsec) VLA radio observations of this cluster are combined with higher resolution (∼2 arcsec) data available in the VLA archive. Results. We discover the presence of a diffuse and extended (∼500 kpc) radio source centered on the cluster, unrelated to the radio emission of the central AGN. The properties of the radio source, in particular a) its occurrence at the center of a massive cooling flow cluster, b) its total size comparable to that of the cooling region, c) its agreement with the observational trend between radio luminosity and cooling flow power, indicate that RX J1347.5-1145 hosts a radio mini-halo. We suggest that the radio emission of this mini-halo, which is the most distant object of its class discovered up to now, is due to electron re-acceleration triggered by the central cooling flow. However, we also note that the morphology of the diffuse radio emission shows an elongation coincident with the position of a hot subclump detected in X-rays, thus suggesting that additional energy for the electron re-acceleration might be provided by the submerger event.

Simulations of galactic winds and starbursts in galaxy clusters

School of Mathematics, University of Edinburgh, Edinburgh EH9 3JZ, Scotland, UK-/-Abstract. We present an investigation of the metal enrichmentof the intra-cluster medium (ICM) bygalactic windsand merger-driven starbursts. We use combined N-body/hydrodynamic simulations with a semi-numerical galaxyformation model. The mass loss by galactic winds is obtained by calculating transonic solutions of steady stateoutflows, driven by thermal, cosmic ray and MHD wave pressure. The inhomogeneities in the metal distributioncaused by these processes are an ideal tool to reveal the dynamical state of a galaxy cluster. We present surfacebrightness, X-ray emission weighted temperature and metal maps of our model clusters as they would be observedby X-ray telescopes like XMM-Newton. We show that X-ray weighted metal maps distinguish between pre- orpost-merger galaxy clusters by comparing the metallicity distribution with the galaxy-density distribution: pre-mergers have a metallicity gap between the subclusters, post-mergers a high metallicity between subclusters. Weapply our approach to two observed galaxy clusters, Abell 3528 and Abell 3921, to show whether they are pre-or post-merging systems. The survival time of the inhomogeneities in the metallicity distribution found in oursimulations is up to several Gyr. We show that galactic winds and merger-driven starbursts enrich the ICM veryefficiently after z=1 in the central (∼ 3 Mpc radius) region of a galaxy cluster.Key words. Galaxies: clusters: general - Galaxies: abundances - Galaxies: interactions - Galaxies: ISM - X-ray:galaxies: clusters

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

Feedback from intra-cluster supernovae on the ICM in cooling flow galaxy clusters

z>2

Multi-wavelength environment of the Galactic globular cluster Terzan 5

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

Finding short GRB remnants in globular clusters: the VHE gamma-ray source in Terzan 5

z<2

Metal enrichment of the intra-cluster medium by thermally and cosmic-ray driven galactic winds - An analytical prescription for galactic outflows

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.

NEW RESULTS FROM H.E.S.S. OBSERVATIONS OF GALAXY CLUSTERS

We study the effect of heating and metal enrichment from supernovae (SNe) residing between galaxies on the Intra-Cluster Medium (ICM). Recent observations indicate that a considerable fraction (∼20%) of the SN Ia parent stellar population in galaxy clusters is intergalactic. By considering their effect on the relaxed progenitors of cooling flow clusters we propose that intra-cluster SNe can act as a distributed heating source which may influence the initial stages of the formation of cooling flows. We investigate the increase in cooling time as a function of the energy input supplied by SNe and their assumed spatial distribution, and conclude that intra-cluster SNe represent a heating source which in some clusters can cause a delay of the formation of cooling flows. This would imply that some cooling flows are younger than previously thought. We also discuss the impact that a large population of intra-cluster SNe could have on the chemical evolution of the ICM in cooling flow clusters.

Long-term remnant evolution of compact binary mergers

Terzan 5 is a Galactic globular cluster exhibiting prominent X-ray and gamma-ray emission. Following the discovery of extended X-ray emission in this object, we explore here archival data at several wavelengths for other unexpected emission features in the vicinity of this globular cluster. Radio data from the Effelsberg 100-m telescope show several extended structures near Terzan 5, albeit with large uncertainties in the flux estimates and no reliable radio spectral index. In particular, a radio source extending from the location of Terzan 5 to the north-west could result from long-term non-thermal electron production by the large population of milli-second pulsars in this globular cluster. Another prominent radio structure close to Terzan 5 may be explained by ionised material produced by a field O star. As for the diffuse X-ray emission found in Terzan 5, its extension appears to be limited to within 2.5 arcmin of the globular cluster and the available multi-wavelength data is compatible with an inverse Compton scenario but disfavours a non- thermal Bremsstrahlung origin.