We present a detailed 2D study of the ionized ISM of IZw18 using new PMAS-IFU optical observations .
IZw18 is a high-ionization galaxy which is among the most metal-poor starbursts in the local Universe .
This makes IZw18 a local benchmark for understanding the properties most closely resembling those prevailing at distant starbursts .
Our IFU-aperture ( \sim 1.4 \times 1.4 kpc ^ { 2 } ) samples the entire IZw18 main body and an extended region of its ionized gas .
Maps of relevant emission lines and emission line ratios show that higher-excitation gas is preferentially located close to the NW knot and thereabouts .
We detect a Wolf-Rayet feature near the NW knot .
We derive spatially resolved and integrated physical-chemical properties for the ionized gas in IZw18 .
We find no dependence between the metallicity-indicator R _ { 23 } and the ionization parameter ( as traced by [ OIII ] / [ OII ] ) across IZw18 .
Over \sim 0.30 kpc ^ { 2 } , using the [ OIII ] \lambda 4363 line , we compute T _ { e } [ OIII ] values ( \sim 15000 - 25000 K ) , and oxygen abundances are derived from the direct determinations of T _ { e } [ OIII ] .
More than 70 \% of the higher- T _ { e } [ OIII ] ( \gtrsim 22000 K ) spaxels are HeII \lambda 4686-emitting spaxels too .
From a statistical analysis , we study the presence of variations in the ISM physical-chemical properties .
A galaxy-wide homogeneity , across hundreds of parsecs , is seen in O/H .
Based on spaxel-by-spaxel measurements , the error-weighted mean of 12 + log ( O/H ) = 7.11 \pm 0.01 is taken as the representative O/H for IZw18 .
Aperture effects on the derivation of O/H are discussed .
Using our IFU data we obtain , for the first time , the IZw18 integrated spectrum .