Galactic Explosions, Radio Galaxies and Quasi-stellar Sources

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Abstract
Earlier theories of radio galaxies and quasi-stellar radio sources are discussed; most fail to account for the large-scale magnetic field which must be frozen into the relativistic gas. An earlier (7) hypothesis attempted to unify normal spiral galaxies and radio galaxies. This is modified and extended to provide a semi-quantitative theory of quasi-stellar sources and other extragalactic radio sources. All may evolve from a contracting, rotating ( ω ) gas cloud in the presence of a large-scale magnetic field ( B ), when ω and B are orthogonal. The field is wound into a spiral of ever increasing strength until electromagnetic forces control the size and shape of the galaxy. Rotational kinetic energy is converted to magnetic energy, so that the balance between gravitational and centrifugal forces is destroyed and contraction may continue to nuclear dimensions. However, at no stage is there a sudden collapse, because rotational energy is steadily replenished from gravitational energy which is the original source of all magnetic, cosmic ray and other energies. The galactic ω dimension is at first much smaller than the disk radius but a spherical stage is reached, followed by an ‘explosion’ along the ± ω axis. A number of such explosions may occur at intervals. At all stages of spirality particles are accelerated in a ‘neutral sheet’ where magnetic field is annihilated. At the explosion stage the rate may be high (time constant ∼10 3 years) and electrons up to cosmic ray energies may be released. ‘Ordinary’ radio galaxies are formed if stars are deposited in galactic orbits by the contracting plasma cloud; quasi-stellar sources result when star formation is inhibited so that the whole galaxy shrinks to a nucleus.

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