  Given the multiple energy loss mechanisms of cosmic ray electrons in
galaxies, the tightness of the infrared - radio continuum correlation is
surprising. We extended the analytical model of galactic disks of Vollmer et
al. (2017) by including a simplified prescription for the synchrotron
emissivity. The galactic gas disks of local spiral galaxies, low-z starburst
galaxies, high-z main sequence starforming, and high-z starburst galaxies are
treated as turbulent clumpy accretion disks. The magnetic field strength is
determined by the equipartition between the turbulent kinetic and the magnetic
energy densities. Our fiducial model, which neither includes galactic winds nor
CR electron secondaries, reproduces the observed radio continuum SEDs of most
(~70%) of the galaxies. Except for the local spiral galaxies, fast galactic
winds can potentially make the conflicting models agree with observations. The
observed IR - radio correlations are reproduced by the model within 2 sigma of
the joint uncertainty of model and data for all datasets. The model agrees with
the observed SFR - radio correlations within ~4 sigma. Energy equipartition
between the CR particles and the magnetic field only approximately holds in our
models of main sequence starforming galaxies. If a CR electron calorimeter is
assumed, the slope of the IR - radio correlation flattens significantly.
Inverse Compton (IC) losses are not dominant in the starburst galaxies because
in these galaxies not only the gas density but also the turbulent velocity
dispersion is higher than in normally starforming galaxies. Equipartition
between the turbulent kinetic and magnetic field energy densities then leads to
very high magnetic field strengths and very short synchrotron timescales. The
exponents of our model SFR - radio correlations at 150 MHz and 1.4 GHz are very
close to one.
