The diffuse ionized gas (DIG) in star-forming galaxies: the influence of aperture effects on local H <scp>ii</scp> regions

The Diffuse Ionized Gas (DIG) contributes to the nebular emission of galaxies, resulting in line flux ratios that can be significantly different from those produced by HII regions. Comparing [SII]6717,31 between pointed observations regions nearby galaxies and integrated spectra more distant it has been recently claimed DIG also deeply affect bright, star-forming a large correction must applied observed recover genuine contribution Here we show instead effect on is lower than assumed previous work. Indeed, aperture effects spectroscopy are largely responsible for difference: when local extracted using enough apertures while still avoiding DIG, same as galaxies. This result highly relevant use strong-line methods measure metallicity.