Wolf-Rayet and RSG stars in M101. I. HST photometry

To this end, we have used the Hubble Space Telescope (HST) to carry out a deep, HeII optical narrowband imaging survey of the ScI spiral galaxy M101. Almost the entire galaxy was imaged with the unprecedented depth and resolution that only the HST affords.

Differenced with archival broadband images, the narrowband images allow us to detect much of the W-R star population of M101. We describe the extent of the survey and our images, as well as our data reduction procedures. A detailed broadband-narrowband imaging study of a field east of the center of M101, containing the giant star-forming region NGC5462, demonstrates our completeness limits, how we find W-R candidates, their properties and spatial distribution, and how we rule out most contaminants.