Infrared line and radio continuum emission of circumstellar ionized regions.

New observations are presented of the hydrogen infrared line emission and radio continuum emission of objects similar to the Becklin-Neugebauer (BN) object in Orion. The radio and hydrogen IR line emission of dense, ionized, flowing stellar envelopes are modeled. The obtained results for the radio continuum flux density, IR line flux, and the rate of recombinations in the envelope are of general applicability. In this case they are applied to the flows associated with young stars still embedded within their molecular clouds. The levels of radio emission and radio spectral index can depend sensitively on the effective Stroemgren radius of the flow. The optical depths in the IR hydrogen lines can be very large. Measurements of relative line strengths can be used to assess the line optical depths. New VLA observations at 1.3 cm, and new Br-gamma, Pf-gamma, and Br-alpha line flux measurements of very compact objects within molecular clouds have been obtained to study the nature of their ionized regions.