The Interstellar Environment of the Wolf-Rayet Star WR 143

Abstract

As part of a systematic study of the environment of Galactic WR stars, a region along the line of sight to Cygnus (l \ 77.5¡, b \ 0¡) has been studied. The neutral hydrogen 21 cm line distribution shows the existence of a cavity expanding from the Wolf-Rayet star WR 143. This cavity, created by the stellar wind of the star, has a mean radius of 7 pc (assuming a distance of about 1 kpc), an expansion velocity of more than 8 km s~1, and a missing mass of some 150 and seems to be surrounded by an H I M _ shell, likely made up of the gas pushed by the star. Although this hole (also called bubble) is quite conspicuous in H I, there seems to be no trace of it at the other wavelengths studied (radio continuum and infrared). All radio observations were obtained at the Dominion Radio Astrophysical Observatory as part of the Canadian Galactic Plane Survey.

The interstellar medium local to HD 10125

“…Several H i voids and shells have been found around massive stars (e.g. Cappa de Nicolau & Niemela 1984; Arnal 1992; Arnal et al 1999; Cappa & Herbstmeier 2000; Cazzolato & Pineault 2000; Arnal 2001; Cichowolski et al 2001). Since the angular resolution in those studies varies from ∼2 to 30–40 arcmin, it is impossible to make a meaningful comparison among the parameters of different H i cavities derived from observations carried out using quite dissimilar instruments.…”

The neutral gas in the environs of the Wolf Rayet stars in the Circinus OB1 association

“…There have been observed other cases where the WR star is overlapping a higher density edge of the associated bubble. See for example the case of WR 143, located close to the dense border of an HI cavity (Cazzolato & Pineault 2000), or the cases of WR 5 and WR 123 (Arnal 1992) with a similar HI morphology. Besides, the fact that WR 65 is a member of Cir OB1 association may explain anomalies in the HI distribution and kinematics.…”

“…Besides, the fact that WR 65 is a member of Cir OB1 association may explain anomalies in the HI distribution and kinematics. As pointed out by Cazzolato & Pineault (2000), OB associations can disturb the ISM by injecting energy into it, producing clouds motions and introducing velocity contamination in the HI data cube. In what follows, we will discuss both features taking into account the possibility that they are physically connected, although the association between the minor HI cavity and the WR 65 star is less convincing.…”

“…These bubbles have been observed as voids in the HI emission distribution in the vicinity of several WR stars (see for example Arnal et al 1999;Cazzolato & Pineault 2000;Cichowolski et al 2001). Generally, these cavities are elongated with the star off-center (Arnal 1992;2001) and often are surrounded by an HI shell (see for example Cappa et al 1996;Gervais & St-Louis 1999).…”

“…Although the large ionizing flux of the WR stars should produce observable thermal radio continuum emission, in many cases it has not been detected (e.g. Cazzolato & Pineault 2000 and references therein). Also non-thermal radio emission associated with WR stars has been detected in only few cases (Chapman et al 1999).…”