The hierarchical fragmentation of a molecular cloud is modelled as a random process by the Monte Carlo method. It is proposed that the IMF for stár formation is bimodal. The probability of the fragmentation in each mode is a function of the initial cloud mass and defined critical mass, which can be derived from the surface
density and temperature of cloud. The modelled IMF is compared with the empirically determined function and the best fit was found for critical masses of 0.3 M^ for low-mass mode and 2.0 M„ for
high-mass mode of star formation.
The Seyfert galaxy NGC I275 circumnuclear region was investigated using spectro- and color photometry which permited us to reveal the region of active starformation near desils, located 3" North-West and 7" North-East from the NGC I275 galaxy nucleus. The mass of these regions HII zones is about 10^6 - 10^7.* and * Abstrakt obsahuje neidentifikovatelný (ručně psaný) symbol.
From photometric and spectrographic observations of the runaway star 53 Ari we confirm that the star did noat exhibit detectable light- and radial velocity variations. The star is definitely not a beta Cephei star.
I. The mean state of circulation in some of the months can be demonstrated by the mean position of the frontal zone. From the position of the frontal zone we can determine if the zonal or meridional circulation prevails, and in which way it will change during the year
II. The long-range variation of the mean frontal zone in relation to solar activity expressed by Ejgenson s Index of Recurrency of Sunspots A is determined. The effect ascertained is especially significant in January. The results in maps show the deviations of frequencies of the zones from the mean state, partly in the years of minima, partly in the years of maxima of the recurrency of sunspots.
An introduction to the theory of no radial modes of oscillations is presented. Evidences of such pulsations can be found in numerous variable stars. We discuss here some new results obtained in stars varying with periods of the order or longer than the hour, namely β Cep stars, line profile variable stars and WR stars.
Vertex deviation in the galactic plane is not compatible with the
Oort-Lindbalad theory about galactic rotation (stationary system with cylindrical symmetry). However, like we show in this work, it can be obtained in a stellar system model that verifies the Chandrasekhar postulates in a non-stationary state, axial symmetry, non-cylindrical, and with an equatorial plane of symmetry.
A number of effects which can affect the low-mass IMF derived from the local luminosity function is studied. We consider an influence of unresolved binairies, variations in fine structure of mass-luminosity relation, BC-scale, chemical composition, and evolution of brown dwarfs. The mass-luminosity relation is found to be the main factor defining the IMF. As analysis shows, different theoretical relations calculated for Pop I composition result in different IMFs /from a power law, to a lognormal one/. The presence at faintest magnitudes /Mν > 20^m/ of a large number of brown dwarfs, slowly evolving with decreasing luminosity, leads to the depletion of the luminosity function for both lognormal and power IMFs.