A deep H$\mathsf{\alpha}$ survey of the Milky Way

Abstract

The Galactic plane has been observed between l= 330 to l= 336 as part of a velocity resolved H survey of the southern Milky Way using a scaning Fabry-Perot on a 36 cm telescope. The detailed analysis of the resultant H profiles reveals the presence of several layers of ionized gas with different velocities over the surveyed region. We have studied in detail both the 2-D spatial and velocity structure of the HII regions RCW102, RCW104 and RCW106. Combining these H observations with stellar and radio data we provide estimates for the most probable distances of these different layers. The first layer at -5 km is local emission linked to the Sco-Cen association at 170 pc. The next layer, around -24 km , is at 1.9 kpc and traces the near section of the Sagittarius-Carina arm. Well connected to the Sagittarius-Carina arm portions traced in the adjacent regions (l= 328 and l= 338 area), the arm, in this longitude range, clearly shows and confirms the departure from a logarithmic spiral. The Scutum-Crux arm is also traced in this area by faint and diffuse emission at -40 km which can be placed at 3.2 kpc. The layer at -52 km is the major spiral-arm feature of the studied area; its most probable stellar distance is 4.2 kpc. An important emission component is also observed at -65 km in the southern part of the surveyed area. This mainly patchy and filamentary emission we identify as the possible optical counterpart of a supernovae remnant centered at l= 332.0, b=-3.2. Finally, two complexes have been determined around 12.5 kpc which places them in the far section of the Norma arm