This paper investigates the group consensus phenomenon for multiple interacting clusters of doubleintegrator agents in the presence of both cooperative and competitive inter-cluster couplings under two different frameworks, viz., the framework that all agents share the same position and velocity interaction topology and the framework that the position and velocity topologies are modeled by tota...

Many galaxies display warps, lopsided images, asymmetric rotation curves or other features which suggest that their immediate dynamical environment is neither static nor in equilibrium. In Cold Dark Matter (CDM) theories, such non-equilibrium features are expected in the inner regions of many dark haloes as a result of recent hierarchical growth. We used the excellent statistics provided by the...

Aims. We investigate the nature of the classical low-velocity structures in the local velocity field, i.e. the Pleiades, Hyades and Sirius moving groups. After using a wavelet transform to locate them in velocity space, we study their relation with the open clusters kinematically associated with them. Methods. By directly comparing the location of moving group stars in parallax space to the iso...

The recently revised cosmological constraints from the Five-Year WMAP data ameliorate previous tension between cosmological constraints from the microwave background and from cluster abundances. We demonstrate that the revised estimates of cosmological parameters are in excellent agreement with the mass function of X-ray clusters in the Sloan Digital Sky Survey. Velocity segregation between gal...

We have used the ARGUS multi–object spectrometer at the CTIO 4m Blanco telescope to obtain 2756 radial velocity measurements for 1966 individual stars in the globular cluster ω Centauri brighter than blue photographic magnitude of about 16.5. Of these, 1589 stars are cluster members. A comparison with two independent radial velocity studies, carried out by Suntzeff & Kraft and by Mayor et al., ...

With the success of the Chandra and XMM missions and the maturation of gravitational lensing techniques, powerful constraints on the orbital structure of cluster dark matter halos are possible. I show that the X-ray emissivity and mass of a galaxy cluster uniquely specify the anisotropy and velocity dispersion profiles of its dark matter halo. I consider hydrostatic as well as cooling flow scen...

We have made CO(J = 2− 1) observations towards the HII region RCW 49 and its ionizing source, the rich stellar cluster Westerlund 2, with the NANTEN2 sub-mm telescope. These observations have revealed that two molecular clouds in velocity ranges of −11 to +9 km s and 11 to 21 km s respectively, show remarkably good spatial correlations with the Spitzer IRAC mid-infrared image of RCW 49, as well...

We consider the conditions required for a cluster core to shrink, by adiabatic accretion of gas from the surrounding cluster, to densities such that stellar collisions are a likely outcome. We show that the maximum densities attained, and hence the viability of collisions, depends on a competition between core shrinkage (driven by accretion) and core puffing up (driven by relaxation effects). T...

We present the discovery of [OIII] 5007 emission associated with the black hole X-ray binary recently identified in a globular cluster in the Virgo elliptical galaxy NGC 4472. This object is the first confirmed black-hole X-ray binary in a globular cluster. The identification of [OIII] 5007 emission from the black-hole hosting globular cluster is based on two independent fiber spectra obtained ...

A proper motion study is presented of the globular cluster ω Centauri. Based on 100 plates obtained with the YaleColumbia 66 cm (26 inch) refractor, and ranging in epoch from 1931 till 1935 and 1978 till 1983, differential proper motions are obtained for 9847 stars. The limiting magnitude (photographic) is 16.0 for the centre of the cluster, 16.5 for the outer parts. The optical system of the Y...