Radio continuum maps at 6 and 20 cm were made from VLA, scaled array observations (A and B configurations at 20 cm and B and C at 6 cm) thus ensuring that all scale lengths of emission are mapped, with nearly identical uv coverage, at a resolution of 1.5" (150 pc). In addition, 2,6 and 20 cm maps (from D, C and B arrays respectively) are utilized to determine the distribution of thermal and nonthermal radiation at resolution of (TURN)4". Optical stellar continuum and emission line imaging are used to separate the stellar populations and to trace the distribution of ionized gas. The synchrotron radiation is found to coincide with the spiral structure as defined by the ionized gas and extreme population I objects. Additionally, the synchrotron emissivity along the arms is shown to be strongly correlated with the spiral shock velocity based on an existing density wave model for NGC 3310. A model for the production of cosmic rays involving supernova remnants is discussed and found to have a number of shortcomings in NGC 3310. A new model for particle acceleration is introduced and discussed. In this scenario, rotational kinetic energy of a galaxy is converted into cosmic rays by global spiral shocks (as modelled by density wave theory) through a diffusive (Fermi-type) shock acceleration mechanism. It differs from previous models in that it is global and uses a readily available energy source. It is shown that the model satisfies all observational constraints. The acceleration mechanism is discussed from a theoretical viewpoint and found to be efficient in galactic disks containing substantial amounts of partially ionized 10('4)(DEGREES)K gas. The efficiency at lower shock velocities is also discussed. The compatibility of the proposed model with observations of nearby galaxies is investigated. It is shown that the model predictions are consistent with the integrated radio continuum properties of grand-design spiral galaxies.
- Pub Date:
- December 1985
- Physics: Astronomy and Astrophysics