THE NGC-7538 IRS-1 REGION OF STAR-FORMATION - OBSERVATIONS OF THE H66-ALPHA RECOMBINATION LINE WITH A SPATIAL-RESOLUTION OF 300-AU

The 1.3 cm continuum and the H66 alpha recombination line emission tow ard NGC 7538 IRS 1 have been imaged with a spatial resolution of 180 a nd 300 AU, respectively. There are several remarkable aspects to the d ata. The core of the H II region is composed of numerous emission clum ps with peak brightness temperatures of approximate to 15,000 K. Extre mely wide line profiles, 250 km s(-1) FWZP, are observed from the core , indicating substantial mass motions of the ionized gas. The H66 alph a spectral profiles exhibit multiple emission peaks. The peaks and sha pes of the H66 alpha recombination line profiles vary significantly as a function of position within the core region. The H66 alpha line-to- continuum ratios also vary considerably within the core region. A thin strip midway between the northern and southern core continuum compone nts is the region of largest electron density. The center of this dens e, disk-like structure most likely delineates the position of the exci ting star. We present a model for NGC 7358 IRS 1 that involves a stell ar wind outflow and photoevaporation of nearby clumpy neutral material . This results in a clumpy continuum appearance and a complicated set of broad- and multiple-peaked spectral profiles. Ionized gas escapes t he core region in an outflow to the north and south. Toward the south the outflow is partially limited by neutral material, producing a sout hern, spherical continuum component which exhibits much narrower H66 a lpha line profiles than the core region.