Spatially resolved study of the physical properties of the ionized gas in NGC 595

We present Integral Field Spectroscopy (IFS) of NGC 595, one of the most luminous H ii regions in M33. This type of observations allows us to study the variation of the principal emission-line ratios across the surface of the nebula. At each position of the field of view, we fit the main emission-line features of the spectrum within the spectral range of 3650-6990 A and create maps of the principal emission-line ratios for the total surface of the region. The extinction map derived from the Balmer decrement and the absorbed H alpha luminosity show good spatial correlation with the 24 mu m emission from Spitzer. We also show here the capability of the IFS to study the existence of Wolf-Rayet (WR) stars, identifying the previously catalogued WR stars and detecting a new candidate towards the north of the region. The ionization structure of the region nicely follows the H alpha shell morphology and is clearly related to the location of the central ionizing stars. The electron density distribution does not show strong variations within the H ii region nor any trend with the H alpha emission distribution. We study the behaviour within the H ii region of several classical emission-line ratios proposed as metallicity calibrators: while [N ii]/H alpha and [N ii]/[O iii] show important variations, the R-23 index is substantially constant across the surface of the nebula, despite the strong variation of the ionization parameter as a function of the radial distance from the ionizing stars. These results show the reliability in using the R-23 index to characterize the metallicity of H ii regions even when only a fraction of the total area is covered by the observations.