We study the morphological content of a large sample of high-redshift clusters to determine its dependence on cluster mass and redshift. Quantitative morphologies are based on PSF-convolved, 2D bulge+disk decompositions of cluster and field galaxies on deep Very Large Telescope FORS2 images of eighteen, optically-selected galaxy clusters at 0.45 < z < 0.80 observed as part of the ESO Distant Cl...

We investigate encounters between giant molecular clouds (GMCs) and star clusters. We propose a single expression for the energy gain of a cluster due to an encounter with a GMC, valid for all encounter distances and GMC properties. This relation is verified with N -body simulations of cluster-GMC encounters, where the GMC is represented by a moving analytical potential. Excellent agreement is ...

The density and velocity fields as extracted from the Abell/ACO clusters are compared to the corresponding fields recovered by the POTENT method from the Mark III peculiar velocities of galaxies. In order to minimize non-linear effects and to deal with ill-sampled regions we smooth both fields using a Gaussian window with radii ranging between 12 − 20 hMpc. The density and velocity fields withi...

We analyze the mass content of the massive strong-lensing cluster Abell 586 (z = 0.17). We use optical data (imaging and spectroscopy) obtained with the Gemini Multi-Object Spectrograph (GMOS) mounted on the 8-m Gemini-North telescope, together with publicly available X-ray data taken with the Chandra space telescope. Employing different techniques – velocity distribution of galaxies, weak grav...

New CORAVEL radial-velocity observations and UBV photometry of 24 red giants in the field of the intermediate-age open cluster Mel 71 are analysed for membership and duplicity. The membership of 16 stars is confirmed, one star is a possible member, and 8 spectroscopic binaries have been discovered , all amongst the cluster stars. Four of their orbits have been determined, with periods ranging f...

We derive analytic expressions for the leading-order corrections to the polarization induced in the cosmic microwave background (CMB) due to scattering off hot electrons in galaxy clusters along the line of sight. For a thermal distribution of electrons with kinetic temperature kBTe ∼ 10 keV and bulk peculiar velocity V ∼ 1000 kms , the dominant corrections to the polarization induced by the pr...

A homogeneous sample of galaxy redshifts in the core regions (R ≤ 0.5 h−1 Mpc) of 12 clusters is used to measure the frequency of substructure with different tests. In 50% of the cases substructure is detected, a frequency which agrees well with previous studies of cluster cores. Magnitude information and rough morphological classes are also available for 80% of the sample, allowing us to confi...

Observations of internal motions in globular clusters offer unique insights into the dynamics of the clusters. We have recently developed methods of high-precision astrometry with HST 's WFPC2 camera, which allow us to measure internal proper motions of individual stars. These new data open up many new avenues for study of the clusters. Comparison of the dispersion of proper motion with that of...

Aims. This paper is aimed at measuring the main physical properties (mass, velocity dispersion, and total luminosity) of the cluster Abell 2163. Methods. Weak lensing analysis is applied to a deep, one square degree r-band CFHT-Megacam image of the Abell 2163 field. The observed shear is fitted with Single Isothermal Sphere and Navarro-Frenk-White models to obtain the velocity dispersion and th...

The rotation of Coulomb clusters with different numbers of micron-sized particles is observed in an inductively coupled dusty plasma in the presence of an axial magnetic field. The rotation is found to be dependent on the particle number and configuration. Clusters with smaller numbers of particles require a higher magnetic field strength in order to initiate the rotation, the threshold magneti...