Related papers: Probing dark matter and galaxy evolution with prop…
It is shown that, owing to the interaction of baryonic matter with the carrier of dark energy, all configurations of baryonic matter acquire energy and inevitably must expand. This conclusion applies to all hierarchical levels of the…
The determination of galaxy cluster mass is of great importance since it is directly linked to the well- known problem of dark matter in the Universe and to the cluster baryon content. X-ray observations from satellites have enabled a…
We show that with a Next Generation Large Telescope one can detect the accelerated motions of ~100 stars orbiting the massive black hole at the Galactic center. The positions and velocities of these stars will be measured to astrometric and…
Measuring the full three-dimensional motions of extra-galactic objects in the Universe presents a seemingly insurmountable challenge. In this paper we investigate the application of a technique to measure tangential motion that has…
We have undertaken a long term program to measure high precision proper motions of nearby Galactic globular cluster (GC) stars using multi-epoch observations with the WFPC2 and the ACS cameras on-board the Hubble Space Telescope. The proper…
Recent advances with the VLBA have resulted in ~10 micro-arcsec astrometry for compact sources in external galaxies, and measurement of the proper motion of Local Group galaxies has been demonstrated. With improved telescopes and equipment,…
We present arguments indicating that galaxies and their clusters should be considered as open developing systems. Galaxies interact with the intergalactic medium and are not in a virial equilibrium (which is determined by the gravity and…
Kinematic studies have produced accurate measurements of the total dark matter mass and mean dark matter density within the optical extent of galaxies, for large samples of objects. Here we consider theoretical predictions for the latter…
We cross-match objects from several different astronomical catalogs to determine the absolute proper proper motions of stars within the 30-arcmin radius fields of 115 Milky-Way globular clusters with the accuracy of 1--2~mas/yr. The proper…
Clusters of galaxies can be used for very different kinds of cosmological tests. I review a few of the methods: determination of cluster masses and dark matter content, metal enrichment and its connection to the origin of the intra-cluster…
We estimate the number of individual, fast-moving stars observable in globular clusters under the assumption that the clusters contain massive central black holes which follow the galactic black-hole mass vs. sigma relationship. We find…
In addition to cosmological tests based on the mass function and clustering of galaxy clusters, which probe the growth of cosmic structure, nature offers two independent ways of using clusters to measure cosmic distances. The first uses…
Despite substantial effort, the precise physical processes that lead to the growth of super-massive black holes in the centers of galaxies are still not well understood. These phases of black hole growth are thought to be of key importance…
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…
We review recent advancements in cosmology with galaxy clusters. Galaxy clusters are the most massive objects in the Universe. Consequently the cluster number density as a function of cluster mass, or cluster abundance, is sensitive to…
X-ray observations of clusters at different redshifts are presented and compared. For the nearest cluster -- the Virgo cluster -- we show a comparison of the galaxy distribution and the distribution of the intra-cluster gas. Although the…
Aims. This work considers the Virgo cluster of galaxies, focusing on its structure, kinematics, and morphological landscape. Our principal aim is to estimate the virial mass of the cluster. For this purpose, we present a sample of 1537…
The next generation X-ray observatory ASTRO-H will open up a new dimension in the study of galaxy clusters by achieving for the first time the spectral resolution required to measure velocities of the intracluster plasma, and extending at…
Primordial black holes might comprise a significant fraction of the dark matter in the Universe and be responsible for the gravitational wave signals from black hole mergers observed by the LIGO/Virgo collaboration. The spatial clustering…
We computed proper motions of a selected sample of globular clusters projected on the central bulge, employing CCD images gathered along the last 25 years at the ESO-NTT, ESO-Danish and HST telescopes. We presented a method to derive their…