RADIAL LIGHT DISTRIBUTIONS IN 5 SPIRAL GALAXIES - THE RELATIONSHIP BETWEEN YOUNG STARS AND THE RELATIVISTIC GAS

The relationship between the young stellar population and the relativi stic gas of five spiral galaxies is examined in this paper. The analys is is based on the comparison of azimuthally averaged radial profiles of H alpha emission, red stellar continuum, and radio continuum emissi on. A direct comparison of the profiles shows that for each galaxy the three light distributions are similar, indicating that all three migh t be driven by the mass profile of the disk. Radial profiles alone are not useful for correlating the relativistic gas with the stellar popu lations. A correlation is found, however, between the mass-normalized (normalized by the red stellar continuum profile) H alpha and radio co ntinuum distributions confirming the existence of a relationship betwe en the relativistic gas and Population I stars. It is found that the m ass-normalized radio continuum profiles are, on average, broader than the Ha profiles. The breadth of the radio profiles is interpreted to b e the result of particle propagation acting to smear out the relativis tic gas distribution relative to the source distribution. A technique is developed to obtain quantitative estimates of the scale length of p article propagation. The scales found range from 0.1 to 2 kpc confirmi ng that propagation effects ''blur'' but do not destroy the signature of the source distribution in the radio data. Our results add further evidence to the hypothesis that the production of relativistic gas in galaxies is associated with the young population of stars.