VLA SPECTRAL-LINE OBSERVATIONS OF THE H-II COMPLEX G34.3+0.2

Four H II regions have been previously detected toward the H II comple x G34.3+0.2 in the radio continuum. Three of these regions (components A, B, and C) are ultracompact. The fourth, G34.3+0.2 component D, is an approximate to 1' (1.1 pc at 3.8 kpc) diameter ringlike H II region . We have observed the H93 alpha radio recombination line emission wit h approximate to 11'' spatial resolution and the 1.3 cm water maser em ission with approximate to 4'' spatial resolution toward G34.3+0.2. Th e observed radio recombination line emission suggests that component D is an expanding shell source. The inferred expansion velocity of 5 km s(-1) gives a calculated lifetime of similar to 10(5) yr. The continu um emission from the source is preferentially brightened on one side. We suggest that this asymmetric brightness distribution may be explain ed by the expansion of the H II region into an anisotropic medium. Alt ernatively, the increased brightness on the northwestern side could be the result of the superposition of two different H II regions. The av erage LSR velocity of the shell source has been determined to be 53.9/-0.1 km s(-1). The observed spatial distribution of the H2O masers in the G34.3+0.2 complex has identified two new regions of star formatio n which are not associated with any radio continuum emission.