N. C. Rana
Articles written in Journal of Astrophysics and Astronomy
Volume 11 Issue 3 September 1990 pp 291-295
The self-consistency of the Einstein Infeld and Hoffman (EIH) equations of motion is critically examined in the limiting case of a threebody problem where two bodies are very close to each other and a third quite far removed from them
Volume 14 Issue 2 June 1993 pp 83-95
We have tried to determine the rate of chemical evolution of high redshift galaxies from the observed redshift distribution of the heavy element absorption systems in the spectra of QSOs, taking into account the evolution in the intensity of the metagalactic UV ionizing radiation background, the radius and/or the co-moving number density of, and the fraction of mass in the form of gas in, the absorbers. The data for both the Lyman limit systems and the C IV systems have been fitted simultaneously. It seems that the abundance of carbon has possibly increased by about a factor of 5 to 20 from the cosmic time corresponding to the redshift ≃ 4 to 2. The data also suggest that either the radius or the co-moving number density of the galaxies increased with redshift up to z = 2.0 and decreased slowly thereafter. The total mass of the halo gas was higher in the past, almost equal to the entire mass of the galaxy at z = 4. The hydrogen column density distribution for Lyman limit systems predicted by the model is in agreement with the observed distribution.
Volume 15 Issue 2 June 1994 pp 187-192
Using the Andersen (1991) data on the mass, absolute visual magnitude, the effective surface temperature and the bolometric corrections, new calibrations for the mass vs. absolute visual magnitude and for the bolometric correction vs. effective surface temperature have been derived. Comparison between the latest evolutionary models with the empirical data has been made to test the evolutionary models for the purpose of stellar population studies.
Volume 15 Issue 2 June 1994 pp 193-196
In view of the recent report on the discovery of low mass halo stars for the candidates of MACHOs, a calculation has been made for the possible enhancement of
Volume 15 Issue 2 June 1994 pp 197-200
A volume-limited sample of F-dwarfs is chosen from Knude (1989) with low radial velocity as well as distance from the sun and compared with the expected model metallicity [Fe/H] distributions, taking the possible chemical inhomogeneity into account. There is found to be an agreement between the two within the error limits of small sampling.
Volume 40 | Issue 5
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