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 ea ch position of the field of view, we fit the main emission-line features of the spectrum within th e spectral range 3650-6990 ˚ A, and create maps of the principal emission-line ratios for th e total surface of the region. The extinction map derived from the Balmer decrement and the absorbed Hluminosity show good spatial correlation with the 24 � m emission from Spitzer. We also show here the capa- bility 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 ion- ization structure of the region nicely follows the Hshell morphology and is clearly related to the location of the central ionizing stars. The electron d ensity distribution does not show strong variations within the H II region nor any trend with the Hemission distribution. We study the behaviour within the H II region of several classical emission-line ratios proposed as metallicity calibrators: while (N II)/Hand (N II)/(O III) show important variations, the R23 index is substantially constant across the surface of the ne bula, despite the strong variation of the ionization parameter as a function of the radial distanc e from the ionizing stars. These re- sults show the reliability in using the R23 index to characterize the metallicity of H II regions even when only a fraction of the total area is covered by the observations.

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