Near-infrared, IFU spectroscopy unravels the bow-shock HH99B

Aims. We aim at characterising the morphology and the physical parameters governing the shock physics of the Herbig-Haro object HH99B. We obtained SINFONI-SPIFFI IFU spectroscopy ( R similar to 2000-4000) between 1.10 and 2.45 mu m detecting more than 170 emission lines, that, to a large extent, have never observed before in a Herbig-Haro object. Most of them come from ro-vibrational transitions of molecular hydrogen (upsilon(up) <= 7, E-up less than or similar to 38 000 K) and [ Fe II] ( Eup less than or similar to 30 000 K). In addition, we observed several hydrogen and helium recombination lines, along with fine-structure lines of ionic species. All the brightest lines appear resolved in velocity. Methods. Intensity ratios of ionic lines were compared with predictions of NLTE models to derive bi-dimensional maps of extinction and electron density, along with estimates of temperature, fractional ionisation, and atomic hydrogen post-shock density. The H-2 line intensities were interpreted in the framework of Boltzmann diagrams, from which we have derived extinction and temperature maps of the molecular gas. From the intensity maps of bright lines ( i.e. H-2 2.122 mu m and [ Fe II] 1.644 mu m), the kinematical properties of the shock(s) at work in the region were delineated. Finally, from selected [ Fe II] lines, constraints on the spontaneous emission coefficients of the 1.257, 1.321, and 1.644 mu m lines are provided. Results. Visual extinction variations up to 4 mag emerge, showing that the usual assumption of constant extinction could be critical. The highest AV is found at the bowhead ( AV similar to 4 mag) while diminishing along the flanks. The electron density increases from similar to 3 x 103 cm(-3) in the receding parts of the shock to similar to 6 x 103 cm(-3) in the apex, where we estimate a temperature of similar to 16 000 K from [ Fe II] line ratios. Molecular gas temperature is lower in the bow flanks ( T similar to 3000 K), then progressively increases toward the head up to T similar to 6000 K. In the same zone, we are able to derive the iron gas-phase abundance (similar to 60% of the solar value) from the [Fe II] 1.257/[P II] 1.187 line ratio, along with the hydrogen fractional ionisation ( up to 50% at the bowhead) and the atomic hydrogen post-shock gas density (similar to 1 x 104 cm(-3)). The kinematical properties derived for the molecular gas substantially confirm earlier ones, while new information ( e. g. vshock similar to 115 km s(-1)) is provided for the shock component responsible for the ionic emission. We also provide an indirect measure of the H-2 breakdown speed ( between 70 and 90 kms(-1)) and compute the inclination angle with respect to the line of sight. The map parameters, along with images of the observed line intensities, will be used to put stringent constraints on up-to-date shock models.