A simple model is constructed to evaluate the change of star formation rate of a disk galaxy due to environmental e†ects in clusters of galaxies. Three e†ects are investigated : (1) tidal force from the potential well of the cluster, (2) increase of external pressure when the galaxy plows into the intracluster medium, and (3) high-speed encounters between galaxies. General analysis indicates th...

We present a numerical investigation of dead, or relic, radio galaxies and the environmental impact that radio galaxy activity has on the host galaxy or galaxy cluster. We perform axisymmetric hydrodynamical calculations of light, supersonic, back-to-back jets propagating in a β-model galaxy/cluster atmosphere. We then shut down the jet activity and let the resulting structure evolve passively....

We study the dependence of galaxy properties on the clustercentric radius and the environment attributed to the nearest neighbor galaxy using the Sloan Digital Sky Survey (SDSS) galaxies associated with the Abell galaxy clusters. We find that there exists a characteristic scale where the properties of galaxies suddenly start to depend on the clustercentric radius at fixed neighbor environment. ...

Star clusters are found in ∼40% of the Local Group galaxies. Their properties are reviewed. The impact of galaxy environment on the evolution and survival of star clusters is discussed. Possible evidence for cluster formation triggered by galaxy interactions, gradients in cluster size, metallicity and stellar content with galactocentric radius and variations as a function of galaxy type are bri...

The results of the analysis of the subclustering in a sample of ESO Nearby Abell Cluster Survey (ENACS) galaxy clusters, with data complemented from other studies, are presented. The analysis is performed by using the S-tree method enabling one to study the hierarchical properties of clusters, namely by the detection of the main physical cluster and of its subgroups. The results indicate: (a) s...

We present a new algorithm to detect inter-cluster galaxy filaments based upon the assumption that the orientations of constituent galaxies along such filaments are nonisotropic. We apply the algorithm to the 2dF Galaxy Redshift Survey catalogue and find that it readily detects many straight filaments between close cluster pairs. At large inter-cluster separations (>> 15h Mpc), we find that the...

1 Abstract We present the results of several surveys for supernovae (SNe) in galaxy clusters. SNe discovered in deep, archival HST images were used to measure the cluster SN Ia rate to z = 1. A search for SNe in nearby (0.06 ≤ z ≤ 0.2) Abell galaxy clusters yielded 15 SNe, 12 of which were spectroscopically confirmed. Of these, 7 are cluster SNe Ia, which we will use to measure the SN Ia rate i...

It is inferred from the symmetrical and luminous X-ray emission of fossil groups that they are mature, relaxed galaxy systems. Cosmological simulations and observations focusing on their dark halo and inter-galactic medium properties confirm their early formation. Recent photometric observations suggest that, unlike the majority of non-fossil brightest group galaxies (BGGs), the central early-t...

The currently most popular models for the dynamical evolution of star clusters predict that the power-law Cluster Luminosity Functions (CLFs) of young star cluster systems will be transformed rapidly into the universal Gaussian CLFs of old Milky Way-type “globular” cluster systems. Here, we provide the first evidence for a turn-over in the intermediate-age, approximately 1 Gyr-old CLF in the ce...

The multiple images observed in galaxy cluster Abell 1689 provide strong constraints not only on the mass distribution of the cluster but also on the ensemble properties of the cluster galaxies. Using parametric strong lensing models for the cluster, and by assuming well motivated scaling laws between the truncation radius s and the velocity dispersion σ of a cluster galaxy we are able to deriv...