Observational constraints on the diffusion of cosmic-ray electrons in spiral galaxies

摘要

We present quantitative tests of the "smearing" model which relates radio and infrared images of spiral galaxies. We test whether the radio image appears as a smeared version of the infrared image in 24 spirals and one irregular, using 20 cm radio images and 60 μm infrared images processed to the same resolution of < ≈1'. Previous work by Bicay & Helou, assuming circularly symmetric, exponentially pro- filed disks, suggested that the smearing function is best approximated by an exponential radial profile. Our detailed assessment of the shape and size of the smearing function is free of those assumptions.