In fl uence of Wolf – Rayet Stars on Surrounding Star-forming Molecular Clouds

Abstract

We investigate the in fl uence of Wolf – Rayet ( W-R ) stars on their surrounding star-forming molecular clouds. We study fi ve regions containing W-R stars in the inner Galactic plane ( l

∼

[ 14 ° – 52 ° ] ) , using multiwavelength data from near-infrared to radio wavelengths. Analysis of 13 CO line data reveals that these W-R stars have developed gas-de fi cient cavities in addition to molecular shells with expansion velocities of a few kilometers per second. The pressure owing to stellar winds primarily drives these expanding shells and sweeps up the surrounding matter to distances of a few parsecs. The column densities of shells are enhanced by a minimum of 14% for one region to a maximum of 88% for another region with respect to the column densities within their central cavities. No active star formation — including molecular condensations, protostars, or ionized gas — is found inside the cavities, whereas such features are observed around the molecular shells. Although the expansion of ionized gas is considered an effective mechanism to trigger star formation, the dynamical ages of the H II

regions in our sample are generally not suf fi ciently long to do so ef fi ciently. Overall, our results hint at the possible importance of negative W-R wind-driven feedback on the gas-de fi cient cavities, where star formation is quenched as a consequence. In addition, the presence of active star formation around the molecular shells indicates that W-R stars may also assist in accumulating molecular gas, and that they could initiate star formation around those shells