The PHANGS-H{\alpha} survey. Ground-based narrow-band imaging of nearby star-forming galaxies

TL;DR

The PHANGS-Hα survey provides high-quality narrow-band imaging of 65 nearby star-forming galaxies, enabling detailed studies of H II regions and star formation rates, and complements other PHANGS multi-wavelength datasets.

Contribution

This work presents the first comprehensive data processing, calibration, and analysis procedures for the PHANGS-Hα survey, enhancing the multi-wavelength study of nearby galaxies.

Findings

Calibrated Hα emission maps for 65 galaxies.

Validated narrow-band photometry against spectroscopic data.

Established best practices for narrow-band Hα imaging analysis.

Abstract

We present PHANGS-H{\alpha}, a narrow-band imaging survey that maps H{\alpha} 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, in 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. PHANGS-H{\alpha} complements the already 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 H ii regions, and star formation rate maps for the bulk of the PHANGS sample. We present observations, data processing, and calibration of the PHANGS-H{\alpha} dataset, as well as the procedures used to derive emission-line fluxes from narrow-band imaging. A subset of galaxies with available spectroscopic Ha mapping from the PHANGS-MUSE survey allows for a detailed comparison with the narrow-band photometry presented here. This informs a series of best practices for the processing of narrow-band H{\alpha} imaging that we apply to the full dataset.