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 complex 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 with approximate to 11'' spatial resolution and the 1.3 cm water maser emission with approximate to 4'' spatial resolution toward G34.3+0.2. The 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 continuum emission from the source is preferentially brightened on one side. We suggest that this asymmetric brightness distribution may be explained by the expansion of the H II region into an anisotropic medium. Alternatively, the increased brightness on the northwestern side could be the result of the superposition of two different H II regions. The average 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 formation which are not associated with any radio continuum emission.