The VLA Development Plan will open new ways to study the
evolution of the radio properties of galaxies with redshift directly.
The strong (i.e., AGN) radio source population clearly evolves with
cosmological epoch- the apparent density of sources increases
rapidly with redshift. This also seems to be true for optically
selected, often radio weak or silent, QSOs. Not far below the 3CR
flux density limit, most sources are at high redshifts (
and
many as high as 
= 3-5). Recently, the IRAS catalog has added a
sample in which dust and molecular emission can be detected beyond
= 2. Closer by, the Hubble Space Telescope has imaged clusters of
galaxies beyond = 0.4, confirming that the Butcher-Oemler effect
(the blueing of cluster galaxy populations with redshift) is related
to increased star formation in clusters at higher redshifts and that
galaxies themselves have different shapes as we look further back.
The direct study of the evolution and possibly the formation of
galaxies appears to be a real possibility. The enhanced VLA would play
a crucial rôle in this arena through detailed exploration of i) the
evolution of radio source populations; ii) molecules, dust and
free-free emission in distant galaxies; iii) starbursts at high
redshifts; and iv) Faraday rotation in magnetized gas-rich
environments.
Technical requirements: