OBSERVATIONS AT 1.4 GHZ IN THE MILKY-WAY BETWEEN LONGITUDE 330-DEGREES AND 340-DEGREES

Observations of recombination lines and continuum emission from 330° to 340° longitude along the Galactic plane at 1.4 GHz are presented. The line was also observed along two cuts perpendicular to the Galactic plane at l = 333° and 334°5. A mean LTE electron temperature of 6700 K is obtained for the region. By using models for different components of an H II region, the origin of the line emission has been studied. As a result, we found that at 1.4 GHz, the observations with the Instituto Argentine de Radioastronomia (IAR) radio telescope are very sensitive to the gas with electron densities between 10 and 100 cm-3, placed at distances less than 5 kpc from the Sun. The contributions to the H 166α line emission originating in low-density gas (Ne < 10 cm-3) come from distances larger than 5 kpc. The gas emission in the H 166α line is associated with Population I material, but it is not always connected to active star-forming regions. Around l = 335°, the recombination lines show evidence of extended interarm ionized gas connecting giant complexes of H II regions situated in Scutum-Crux and Norma arms. For this gas, an upper limit of 200 K for the electron temperature and a mean electron density of 0.07 cm-3 are obtained. Between l = 338° and 339°, we found an extended weak emission with radial velocity of -120 km s-1. The feature is well correlated with CO emission. From our analysis, we conclude that the mission comes from a diffuse ionized cloud of 5 × 104 M⊙ located in the 3 kpc expanding arm. The gas in the direction of PSR 1641-45 is discussed. The radial distributions of the H 166α recombination line in the south quadrant are governed by the emission arising from 330°-340° longitude. The emitting region is located at galactocentric distances between R/Ro = 0.5 and 0.9. Assuming that the emitting gas is smooth in the Galaxy, the upper limit of 150 pc was obtained for the scale height for the ionized gas.