ﻻ يوجد ملخص باللغة العربية
We analysed the fine structure of the phase space distribution function of nearby subdwarfs using data extracted from various catalogues. Applying a new search strategy based on Dekkers theory of galactic orbits, we found four overdensely populated regions in phase space. Three of them were correlated with previously known star streams: the Hyades-Pleiades and Hercules streams in the thin disk of the Milky Way and the Arcturus stream in the thick disk. In addition we find evidence for another stream in the thick disk, which resembles closely the Arcturus stream and probably has the same extragalactic origin.
We have analyzed the phase space distribution of a sample of about 900 non--kinematically selected low metallicity stars in the solar vicinity. The stars primarily represent the thick disk and halo populations of the Milky Way. We aim to identify ove
Multi-epoch radio-interferometric observations of young stellar objects can be used to measure their displacement over the celestial sphere with a level of accuracy that currently cannot be attained at any other wavelength. In particular, the accurac
We present an analysis of the properties of HI holes detected in 20 galaxies that are part of The HI Nearby Galaxy Survey (THINGS). We detected more than 1000 holes in total in the sampled galaxies. Where they can be measured, their sizes range from
This thesis describes a detailed investigation of the effects of matter inhomogeneities on the cosmological evolution of the fine structure constant using the Bekenstein-Sandvik-Barrow-Magueijo (BSBM) theory. We briefly review the observational and t
A volume limited and absolute magnitude limited sample of A-F type dwarfs within 125 parsecs of the Sun is searched for inhomogeneities in the density- velocity space, expecting signatures of the cluster evaporation, phase mixing and possible disc he