A DRAO and VLA Investigation of the Environment of WR 130

CICHOWOLSKI SILVINA; PINEAULT SERGE; ARNAL E. MARCELO; TESTORI J. C.; GOSS, M.; CAPPA CRISTINA E.

ASTRONOMICAL JOURNAL

Año: 2001 vol. 122 p. 1938 - 1953

0004-6256

The environment of the Wolf-Rayet (WR) star WR 130 has been studied using the 21 cm H I line and radio continuum data at 408 and 1420 MHz obtained with the Dominion Radio Astrophysical Observatory (DRAO) Synthesis Telescope. In addition, the H110α recombination line and 21 cm H I line were observed using the Very Large Array in the DnC and D configurations. The Sharpless H II region, Sh 98 (size ~15'), and two OB stars are observed near the Wolf-Rayet star position. An extended ring-shaped structure (G68.1+1.1) of size ~20' is observed in the radio continuum and infrared data. Of four compact radio sources seen superposed on the ring, one is an H II region of size ~3' (G68.14+0.92), while the others are probably extragalactic. The spectral index (Sν~να) of G68.1+1.1 is α=0.0+/-0.1. The thermal nature of G68.1+1.1 is confirmed by an analysis of the correlation between the brightness temperature at 21 cm and the brightness at 60 μm, as observed with IRAS. The DRAO H I data show an H I bubble in the velocity range -12 to 1 km s-1. The most striking characteristic of the H I cavity is the excellent correlation with the radio continuum ring. The WR star is not at the center of the ring, but in the dense border to the east. This eccentric position can be explained by a combination of a high spatial velocity for the star and projection effects. The possible contribution of the OB stars present in the area is also considered. From our H110α observations, together with other recombination lines observed in the area, we deduce a distance of 12 kpc for the compact H II region G68.14+0.92 and 5 kpc for G68.1+1.1. We conclude that G68.1+1.1 is the radio counterpart of the optical H II region Sh 98, while G68.14+0.92 is a chance superposition of a much more distant source. The ionized mass of the ring is estimated at ~3000 Msolar and the rms electron density at ~3 cm-3, assuming a homogeneous distribution. A missing H I mass of 500 Msolar is obtained for the cavity and an excess H I mass of 1500 Msolar for the shell.