The UV-IR Energy Budget and Far-Infrared Emission in Spiral Galaxies
Session 106 -- Galaxies: Photometry and Spectrophotometry
Display presentation, Thursday, 12, 1995, 9:20am - 6:30pm

## [106.15] The UV-IR Energy Budget and Far-Infrared Emission in Spiral Galaxies

L.V. Jones and W.C. Keel (U. Alabama)

We use available ultraviolet imagery and HIRES processing of IRAS data to examine the energy balance in spatially-resolved spiral galaxies, using the UV data to constrain the dominant energy input to the dust more tightly than possible from optical data. The improved resolution of the HIRES output allows separation of individual clumps of star-forming regions in the disks of nearby galaxy, so that we can start to approach a point-by-point comparison of stellar energy input and FIR reradiation. The availability of UV fluxes for many of these clumps allows us to map the input UV radiation field more accurately than is possible either from optical colors or use of H$\alpha$ emission (which is insensitive to stars later than about B0).

For the disks of Sc galaxies, we find (in agreement with earlier work) that young hot stars dominate the dust heating. In the central parts of the Sb galaxy M81, additional heating (presumably from the more intense optical starlight, since the AGN is very weak) is necessary, much as found for several other early-type galaxies from KAO observations.