The H-alpha emission of the spiral galaxy NGC 7479

We use the catalogue of HII regions obtained from a high quality continuum- subtracted H-alpha image of the grand-design spiral galaxy NGC 7479, to con struct the luminosity function (LF) for the HII regions (over 1000) of the whole galaxy. Although its slope is within the published range for spirals of the same morphological type, the unusually strong star formation along t he intense bar of NGC 7479 prompted us to analyse separately the HII region s in the bar and in the disc. We have calculated the physical properties of a group of HII regions in the bar and in the disc selected for their regul ar shapes and absence of blending. We have obtained galaxy-wide relations f or the HII region set: diameter distribution function and also the global H -alpha surface density distribution. As found previously for late-type spir als, the disc LF shows clear double-linear behaviour with a break at log L- H alpha similar to 38.6 (in erg(-1)). The bar LF is less regular. This refl ects a physical difference between the bar and the disc in the properties o f their populations of regions.