VLA and Effelsberg observations of the interstellar medium around the runaway star WR 124

Abstract

Aims:We present very large array (VLA) and Effelsberg radio continuum and 21 cm H I line observations of the interstellar medium (ISM) surrounding the runaway star WR 124 and the nebula M 1-67. The H I data have been used to investigate the effects that a star with a strong stellar wind and a high peculiar velocity has on the ISM.
Methods: The VLA 21 cm H I observations were combined with single-dish Effelsberg observations to produce a series of H I images sensitive to all angular scales from the VLA resolution limit (∼ 46'') up to the primary field of individual VLA antennae (FWHM = 36'). MSX and IRIS images were used to analyze the infrared emission around the star. Because the star is highly supersonic with respect to its local ISM, the observed H I distribution around the star is interpreted in terms of a simple bow shock model.
Results: The analysis of the H I data reveals the presence of a cavity centered on the star at an LSR velocity of ∼ 60 km s^-1, consistent with a distance estimate of 5 kpc for WR 124. A second H I cavity is observed located 10' to the north of the stellar position, consistent with the direction of motion of WR 124. The VLA continuum image at 8.5 GHz shows a remarkable resemblance to the optical images. All available radio continuum data suggest a purely thermal spectrum for the nebula. The MSX and IRIS infrared data show a changing morphology with wavelength. The dust temperature deduced from the infrared luminosities is in agreement with previous observations of bow shocks.