Lifetime of electrons (in yr) emitting at 1.4 GHz, as a function of the particle number density (in cm⁻³), and subjected to bremsstrahlung (long dashes), ionization (short dashes), synchrotron (solid line), and inverse Compton (dash-dotted line) losses. Synchrotron and inverse Compton losses are appropriate for the A nucleus. We note that at low particle densities, which are appropriate for most extra-nuclear regions in galaxies, radiative losses (i.e. synchrotron and IC) dominate, while at high particle densities like those encountered in the nuclear regions of LIRGs, bremsstrahlung and ionization losses dominate (see main text for details).