Stages Of Galactic Evolution Research Articles

The Impact of Nucleosynthesis Models on Models of the Chemical Evolution of Disk Galaxies

The impact of uncertainties in the relative efficiency of nucleosynthesis of various elements in stars on models of the chemical evolution of disk galaxies is studied using a single-zone model for the galactic evolution. The dependences of the abundances of 12C, 14N, 16O, and 56Fe on nucleosynthesis models are compared. The influence of the uncertainty in iron production by Type Ia supernovae on its abundance in a galaxy is also considered. It is concluded that differences in nucleosynthesis models can appreciably affect the results of modeling the early stages of galactic evolution, but this influence becomes insignificant at ages t> 109 yr. Uncertainties in the amount of iron ejected by Type Ia supernovae do not significantly influence the total galactic abundance of iron.

Cosmological magnetic helicity

AbstractWe argue that magnetic helicity conservation is violated at the lepton stage in the evolution of the early Universe. As a result, a cosmological magnetic field which can be a seed for the galactic dynamo obtains a substantial magnetic helicity from the beginning which has to be taken into account on later stages of galactic evolution. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Hierarchial galactic dynamo and seed magnetic field problem

A new approach to the galactic seed magnetic field problem is briefly discussed. It is shown that, in early stages of galactic evolution, the hierarchial agglomeration and fragmentation processes can account for the generation of a dynamically important magnetic field. The amplification of this field follows an inverse cascade since a non-zero average value of the field amplified on a smaller scale serves as a seed field on the next (earlier) hierarchial scale. In such a scenario, a problem of how to get things started never occurs as any infinitesimally small battery generated seed field (Lazarian 1992a) can be efficiently amplified passing by through a sufficient number of amplification cascades.

FORMATION OF A GIANT GALACTIC GASEOUS HALO: METAL-ABSORPTION LINES AND HIGH-VELOCITY CLOUDS

FORMATION OF A GIANT GALACTIC GASEOUS HALO: METAL-ABSORPTION LINES AND HIGH-VELOCITY CLOUDS

Gravitational Separation of Elements During Certain Stages of Galactic Evolution

Heavy metal content is, apart from the kinematical behaviour, one of the important parameters of the population characteristics of stars. Spectroscopic observations of some galaxies including our own give the evidence for the gradient of heavy elements abundances towards the galactic center and the galactic plane (Peimbert 1975, Van den Bergh 1975 review papers). Simultaneously several authors (Kuroczkin 1974, Khokhlova 1976) found that the deficiency (or enrichment) increase with the mass number of the element.