SIMBAD references

The detailed velocity field of the ionized hydrogen over an area of about 4x3deg around galactic longitude 328deg has been obtained in the frame of an Hα Survey of the galactic plane carried out at ESO La Silla. The detailed analysis of the Hα profiles shows that there are several layers of ionized hydrogen with different velocities. Besides individual HII regions there are two diffuse nebular emissions detected all over the studied area with velocities -20km/s and -40km/s. The HII regions exhibit complex structures; according to their velocities they can be divided into two groups around -40km/s and -47km/s. We have studied in detail the structure 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 Hα data allow us to determine the distances of the nebular components. We find that the faint ionized gas layer at -20km/s, never detected before, neither at optical nor at radio wavelengths, is at about 1kpc and defines the Sagittarius Carina arm at longitude 328deg. This implies that the main HII regions in this area and the diffuse ionized hydrogen in which they are immersed belong to a second arm (probably the Scutum Crux arm). This arm appears split at this longitude with two groups at 2.3 and 3kpc. The radiosource 327.759-0.351 at H109α V_LSR=-72km/s (d_kin=4.5kpc) has been detected at Hα wavelength behind the other Hα emissions.