Galactic radio astronomy spans an extraordinary range of astrophysical phenomena: from protostars and their nurseries to pre-main sequence objects; the full range of main sequence stars-including the winds of O stars, the magnetospheres of the Bp stars, and the coronae of late-type stars; post-main sequence objects such as the red giant stars and systems containing a degenerate object-pulsars, cataclysmic variables, and X-ray binaries; and stars at their life's end-planetary nebulae and supernova remnants. But galactic radio astronomy includes far more than the study of stellar constituents. Of critical importance to understanding the Galactic ``ecosystem'' and its evolution is the study of ionized, atomic, and molecular gas, of dust, and of Galactic magnetic fields.
The observational problems posed by Galactic radio astronomy are as broad as the range of phenomena under study. Objects include the highly transient (pulsars, flare stars, X-ray transients) to the ``static'' (H II regions); pointlike objects (main sequence stars) to highly extended emission (SNRs, H I emission); purely continuum sources (SNRs) to those requiring a powerful spectrometer (masers, radio recombination lines).
The VLA has addressed many of these observational problems with extraordinary effectiveness over the past 15 years. During this time the field of stellar radio astronomy has come into its own, with roughly 30% of the VLA observing time being devoted to stellar objects at present. The VLA discovered the spectacular complexity of the Galactic Center, superluminal sources in our own galaxy. It has also made many other significant discoveries and contributions in almost every area of Galactic research.
This chapter discusses the many limitations now confronting Galactic observers and explores the impact of the VLA Development Plan in this arena. It shows that, in some areas, we could make major progress with only incremental improvements to the instrument (e.g., completion of the 40-50 GHz band). It also shows that the fully enhanced VLA (e.g., the wide bandwidths combined with the A+ configuration) will open entirely new areas of observational radio astronomy via sensitive high resolution imaging of thermal emission.