We present a narrowband imaging survey that maps Hα emission over a sample of 65 nearby massive star-forming galaxies. The data were obtained using the MPG-ESO 2.2-meter telescope at La Silla and the du Pont 2.5-meter telescope at Las Campanas Observatory, within the framework of the multi-wavelength cloud-scale (50--100 pc) resolution mapping of molecular gas and star formation conducted by the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) collaboration. complements the published PHANGS-ALMA, PHANGS-MUSE, PHANGS-HST, and PHANGS-JWST surveys, providing an anchor point for the photometric and astrometric calibration of these datasets, as well as samples of ̋ii regions and star formation rate maps for the bulk of the PHANGS sample. We describe the observations, data processing, and calibration of the dataset, as well as the procedures used to derive emission-line fluxes from narrowband imaging. A subset of galaxies with available spectroscopic Ha mapping from the PHANGS-MUSE survey serves as the basis of a detailed comparison with the narrowband photometry presented here. This comparison informs a set of best practices for the processing of narrowband Hα imaging, which we subsequently apply to the full dataset.
Razza et al. (2026) studied this question.