Context :

Aims : We present an integral field spectroscopic study with the Gemini Multi-Object Spectrograph ( GMOS ) of the unusual blue compact dwarf ( BCD ) galaxy Mrk 996 .

Methods : We show through velocity and dispersion maps , emission-line intensity and ratio maps , and by a new technique of electron density limit imaging that the ionization properties of different regions in Mrk 996 are correlated with their kinematic properties .

Results : From the maps , we can spatially distinguish a very dense high-ionization zone with broad lines in the nuclear region , and a less dense low-ionization zone with narrow lines in the circumnuclear region .
Four kinematically distinct systems of lines are identified in the integrated spectrum of Mrk 996 , suggesting stellar wind outflows from a population of Wolf-Rayet ( WR ) stars in the nuclear region , superposed on an underlying rotation pattern .
From the intensities of the blue and red bumps , we derive a population of \sim 473 late nitrogen ( WNL ) stars and \sim 98 early carbon ( WCE ) stars in the nucleus of Mrk 996 , resulting in a high N ( WR ) / N ( O+WR ) of 0.19 .

We derive , for the outer narrow-line region , an oxygen abundance 12+log ( O/H ) =7.94 \pm 0.30 ( \sim 0.2 Z _ { \odot } ) by using the direct T _ { e } method derived from the detected narrow [ O iii ] \lambda 4363 line .
The nucleus of Mrk 996 is , however , nitrogen-enhanced by a factor of \sim 20 , in agreement with previous CLOUDY modeling .
This nitrogen enhancement is probably due to nitrogen-enriched WR ejecta , but also to enhanced nitrogen line emission in a high-density environment .
Although we have made use here of two new methods - Principal Component Analysis ( PCA ) tomography and a method for mapping low- and high-density clouds - to analyze our data , new methodology is needed to further exploit the wealth of information provided by integral field spectroscopy .

Conclusions :