THE SAGITTARIUS-B2 STAR-FORMING REGION .1. SENSITIVE 1.3 CENTIMETER CONTINUUM OBSERVATIONS

The radio continuum toward the Sgr B2 region of star formation has bee n imaged at a wavelength of 1.3 cm with a spatial resolution of approx imate to 2000 AU (0 ''.(25) and a sensitivity of approximate to 0.4 mJ y beam(-1). These high-quality images show many newly detected continu um components and reveal remarkable features associated with several p reviously known H II regions. Current models of ultracompact H II regi ons are discussed within the context of these new data. The images det ail 49 individual continuum components within the Sgr B2 complex. Half of these have diameters less than 5000 AU, including several unresolv ed components (diameters < 2100 AU). These H II regions may be explain ed by a disk photoevaporation model. There are many asymmetrically bri ght shell-like and arclike H II regions in Sgr B2. The asymmetries obs erved in the 1.3 cm continuum from these shell-like and arclike H II r egions correspond to gradients in the 20 cm --> 1.3 cm spectral indice s, reflecting gradients in the electron densities within many of these H II regions. These shell- and arclike sources may be best described by an ''improved'' champagne flow model, incorporating stellar winds a nd significant gradients in the density of ambient neutral material. N umerous filamentary structures are seen in images of the long-tail com etary H II region Sgr B2 I. At least three components are identified i n the tail region exhibiting two different position angles on the plan e of the sky. The morphology may result from an interaction between th e ionized gas of Sgr B2 I and external winds which originate within th e nearby Sgr B2 F cluster of H II regions.