  We have performed 23 GHz VLA observations of 7 compact, luminous infrared
galaxies, selected to have evidence of starburst activity. New and published
multi-frequency data are combined to obtain the spectral energy distributions
of all 7 galaxies from the near-infrared to the radio (at 1.4 GHz). These SEDs
are compared with new models, for dust enshrouded galaxies, which account for
both starburst and AGN components. In all 7 galaxies the starburst provides the
dominant contribution to the infrared luminosity; in 4 sources no contribution
from an AGN is required. Although AGN may contribute up to 50 percent of the
total far--infrared emission, the starbursts always dominate in the radio. The
SEDs of most of our sources are best fit with a very high optical depth of
(>=50) at 1 micron. The scatter in the far-infrared/radio correlation, found
among luminous IRAS sources, is due mainly to the different evolutionary status
of their starburst components. The short time-scale of the star formation
process amplifies the delay between the far-infrared and radio emission. This
becomes more evident at low radio frequencies (below about 1 GHz) where
synchrotron radiation is the dominant process. In the far-infrared (at
wavelengths shorter than 100 micron) an additional source of scatter is
provided by AGN, where present. AGN may be detected in the near-infrared by the
absence of the knee, typical of stellar photospheres. However, near-infrared
data alone cannot constrain the level at which AGN contribute because the
interpretation of their observed properties, in this wave-band, depends
strongly on model parameters.
