HI bubbles surrounding southern optical ring nebulae: Anon (WR 23) and RCW 52

Abstract

We analyze the interstellar medium in the environs of two hot and massive stars, HD 92809 (=WR 23, WC6) and LSS 1887 (O8V), which ionize the optical ring nebulae Anon (WR 23) and RCW 52, respectively. Our analysis is based on neutral hydrogen (HI) 21 cm line data, which reveal interstellar bubbles surrounding the massive stars and their optical ring nebulae. The HI bubble related to WR 23 is 13.3 pc in radius and is expanding at 10 km s-1. The associated atomic neutral mass is 830 M⊙. The HI structure related to LSS 1887 is about 6.3 pc in radius, has an expansion velocity of 7 km s-1 and an associated atomic neutral mass of 100 M⊙. These HI features are the neutral counterparts of the optical ring nebulae and were mainly created by the action of the stellar winds of the massive stars on their environs. The dynamical age of the HI bubble around WR 23 (7 × 10 5 yr) suggests that it was created during the WR phase of stellar evolution. However, the large tangential motions of WR 23 and LSS 1887 suggest that part of the observed optical and HI structures may be due to a bow shock. The analysis of the distribution of emission in the far infrared and in the CO(1-0) molecular line in the environs of WR 23 and LSS 1887 reveals that there are also infrared and molecular counterparts of the detected HI bubbles.