Galactic Evolution of Light Elements: Theoretical Analysis

Abstract

Evolution of deuterium, helium, CNO- and heavy elements in galaxies is numerically simulated taking into account stellar activity (different in spiral and elliptical galaxies), galactic ejection and accretion on to the galaxies. Different forms of initial mass function and star formation rate are used. Observations of light and heavy elements in galaxies and intergalactic gas are used as tests for verification of the obtained theoretical results. Analysis of the model versions corresponding to these observations leads to the conclusions: i) initial mass function should be time-dependent due to enrichment of interstellar medium by heavy elements; ii) factor of deuterium astration in galaxy is ≲ 2, that is mainly due to accretion on to the galaxy; iii) rates of galactic enrichment by helium and heavy elements evolve differently that leads to dependence of the value ∆Y/Z on the galaxy lifetime.