1995A&AS..114..557R

We have observed with a Fabry-Perot interferometer in Hα light 7 fields, 38'x38' each, covering the galactic HII regions S 299, 300, 302, 305, 306, 307 and 309 (231deg<l<235deg, -1deg<b<2deg). The Hα profiles consist of emission lines of several layers of ionized gas superimposed along the line of sight, with different radial velocities. The discrete HII regions of this area may be separated into two velocity groups, V_LSR∼16km/s and V_LSR ∼43km/s. Two of them (S 305 and S 307) show a peculiar velocity with respect to their associated molecular cloud which may be explained by a "Champagne effect". The Hα profiles observed in zones without HII region show that there are two layers of diffuse emission all over this galactic area, with the same velocities as the HII regions. The two groups of ionized gas are associated with giant molecular clouds of similar velocity. Spectrophotometry of exciting stars of HII regions enables one to determine the distance of both complexes quite accurately since we average several individual HII region distances. The first complex is found at 2.1kpc whereas the second one is found at 4.2kpc corresponding to galactocentric distances of 9.9 and 11.5kpc with R_o=8.5kpc.