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The local luminosity function was determined at v = 1. 4 GHz from radio observations of two low-redshift galaxy samples: (1) spiral and irregular galaxies with apparent blue magnitudes BT_ = -45ᵈeg^ and (2) galaxies of all morphologies with blue angular diameters θM_ >= 1. 0' in the declination range -2. 5ᵈeg^ <= δ <= +82ᵈeg^. Separate luminosity functions for the radio source populations powered by "starbursts" and "monsters" were obtained from the latter sample. Locally these two energy sources contribute almost equally to the 1. 4 GHz spectral power density (U ~ 2 x 10¹9^ W Hz^-1^ Mpc^-3^ and U ~ 3 x 10¹9^ W Hz^-1^ Mpc^-3^, respectively, for H₀_ = 50 km s^-1^ Mpc^-1^). The new luminosity functions and the counts of faint (S <= 1 mJy) radio sources found at v = 1. 4 GHz together imply strong cosmological evolution of sources fainter than L ~ 10²4^ W Hz^-1^. This evolution is so strong that most features of the observed radio source counts and redshift distributions can be explained by a remarkably simple evolutionary model that places all radio sources in a hollow spherical shell at z ~ 0. 8.
J. J. Condon (Wed,) studied this question.