H II region candidates in NGC628

This is the first paper of a series dedicated to nebular physics and the chemical evolution of nearby galaxies by investigating large samples of H II regions with the Canada-France-Hawaii Telescope imaging spectrograph SITELLE (Spectro-Imageur a Transformee de Fourier pour l'Etude en Long et en Large des raies d'Emission). We present a technique adapted to imaging spectroscopy to identify and extract parameters from 4285 H II region candidates found in the disc of NGC 628.

Using both the spatial and spectral capabilities of SITELLE, our technique enables the extraction of the position, dust extinction, velocity, H{alpha} profile, diffuse ionized gas (DIG) background, luminosity, size, morphological type, and the emission-line fluxes for individual spaxels and the integrated spectrum for each region. We have produced a well-sampled H II region luminosity function and studied its variation with galactocentric radius and level of the DIG background.