DEEP H-ALPHA SURVEY OF THE MILKY-WAY .2. THE L=328-DEGREES AREA

The detailed velocity field of the ionized hydrogen over an area of ab out 4 degrees x 3 degrees around galactic longitude 328 degrees has be en obtained in the frame of an H alpha Survey of the galactic plane ca rried out at ESO La Silla. The detailed analysis of the H alpha profil es shows that there are several layers of ionized hydrogen with differ ent velocities. Besides individual HII regions there are two diffuse n ebular emissions detected all over the studied area with velocities -2 0 km s(-1) and -40 km s(-1). The HII regions exhibit complex structure s; according to their velocities they can be divided into two groups a round -40 km s(-1) and -47 km s(-1). We have studied in detail the str ucture and velocities of the bright HII regions. The well known narrow lines of RCW94 are confirmed. The distances of the O-B3 stars in this area have been calculated from the literature data, and combined with radio data and our H alpha data allow us to determine the distances o f the nebular components. We find that the faint ionized gas layer at -20 km s(-1), never detected before, neither at optical nor at radio w avelengths, is at about 1 kpc and defines the Sagittarius Carina arm a t longitude 328 degrees. This implies that the main HII regions in thi s area and the diffuse ionized hydrogen in which they are immersed bel ong to a second arm (probably the Scutum Crux arm). This arm appears s plit at this longitude with two groups at 2.3 and 3 kpc. The radiosour ce 327.759 - 0.351 at H109 alpha V-LSR = -72 km s(-1) (d(kin) = 4.5 kp c) has been detected at Ha wavelength behind the other H alpha emissio ns.