Evolution of Galaxies and Secular Variation of Cosmic Rays, Magnetic Fields and Turbulence

概要

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Numerical computations of evolution of galaxies are made on the assumption that the galaxies are the homogeneous mixture of gas and stars with constant volume and that the stellar birth rate depends not only on the density but also on the temperature of gas in the galaxies. Evolutional changes of the luminosity, the mass of gas, the temperature, the chemical composition, and the energy densities of cosmic rays, magnetic fields, turbulence, radiation fields and thermal energy are calculated. The results show that the time variation of these quantities are rather small because negative feedback operates. The luminosities change a factor of ten and a factor of two in the case of elliptical galaxies and spiral galaxies, respectively. The energy densities of cosmic rays, magnetic fields and turbulence are found to be nearly equal and about 10^<-12> erg cm^<-3> and the energy densities of radiation fields are also about 10^<-12> erg cm^lt-3> at the time 10^<10> years. This result agrees well with observations. Model galaxies with various initial densities of gas are examined, and it is concluded that the Hubble types of galaxies are not evolutional sequence but the initial gas density determines the types of galaxies, as was suggested by Holmberg.
一般社団法人日本物理学会の論文
1970-06-25