H II Shells Surrounding Wolf-Rayet Stars in M31

We present the results of an ongoing investigation to provide a detailed view of the processes by which massive stars shape the surrounding interstellar medium (ISM), from parsec to kiloparsec scales. In this paper, we focus on studying the environments of Wolf-Rayet (W-R) stars in M31 to find evidence for W-R wind-ISM interactions, through imaging ionized hydrogen nebulae surrounding these stars. We have conducted a systematic survey for H II shells surrounding 48 of the 49 known W-R stars in M31. There are 17 W-R stars surrounded by single shells, or shell fragments, seven stars surrounded by concentric, limb-brightened shells, 20 stars where there is no clear physical association of the star with nearby Hα emission, and four stars that lack nearby Hα emission. Of the 17+7 shells above, there are 12 that contain one or two massive stars (including a W-R star) and that are <=40 pc in radius. These 12 shells may be classical W-R ejecta or windblown shells. Further, there may be excess Hα point-source emission associated with one of the 12 W-R stars surrounded by putative ejecta or windblown shells. There is also evidence for excess point-source emission associated with 11 other W-R stars. The excess emission may arise from unresolved circumstellar shells or within the extended outer envelopes of the stars themselves. In a few cases, we find clear morphological evidence for W-R shells interacting with each other. In several Hα images, we see W-R winds disrupting, or punching through, the walls of limb-brightened H II shells.