We investigate the 2D excitation structure of the ISM in a sample of LIRGs and Seyferts using near-IR IFS. This study extends to the near-IR the well-known optical and mid-IR emission line diagnostics used to classify activity in galaxies. Based on t
he spatially resolved spectroscopy of prototypes, we identify in the [FeII]1.64/Br$gamma$ - H_2 1-0S(1)/Br$gamma$ plane regions dominated by the different heating sources, i.e. AGNs, young MS massive stars, and evolved stars i.e. supernovae. The ISM in LIRGs occupy a wide region in the near-IR diagnostic plane from -0.6 to +1.5 and from -1.2 to +0.8 (in log units) for the [FeII]/Br$gamma$ and H_2/Br$gamma$ line ratios, respectively. The corresponding median(mode) ratios are +0.18(0.16) and +0.02(-0.04). Seyferts show on average larger values by factors ~2.5 and ~1.4 for the [FeII]/Br$gamma$ and H_2/Br$gamma$ ratios, respectively. New areas and relations in the near-IR diagnostic plane are defined for the compact, high surface brightness regions dominated by AGN, young ionizing stars, and SNe explosions, respectively. In addition, the diffuse regions affected by the AGN radiation field cover an area similar to that of Seyferts, but with high values in [FeII]/Br$gamma$ that are not as extreme. The extended, non-AGN diffuse regions cover a wide area in the diagnostic diagram that overlaps that of individual excitation mechanisms (i.e. AGN, young stars, and SNe), but with its mode value to that of the young SF clumps. This indicates that the excitation conditions of the diffuse ISM are likely due to a mixture of the different ionization sources. The integrated line ratios in LIRGs show higher excitation conditions i.e. towards AGNs, than those measured by the spatially resolved spectroscopy. If this behaviour is representative, it would have clear consequences when classifying high-z, SF galaxies based on their near-IR integrated spectra.
The barred grand-design spiral M83 (NGC 5236) is one of the most studied galaxies given its proximity, orientation, and particular complexity. Nonetheless, many aspects of the central regions remain controversial conveying our limited understanding o
f the inner gas and stellar kinematics, and ultimately of the nucleus evolution. In this work, we present AO VLT-SINFONI data of its central ~235x140 pc with an unprecedented spatial resolution of ~0.2 arcsec, corresponding to ~4 pc. We have focused our study on the distribution and kinematics of the stars and the ionised and molecular gas by studying in detail the Pa_alpha and Br_gamma emission, the H_2 1-0S(1) line at 2.122 micron and the [FeII] line at 1.644 micron, together with the CO absorption bands at 2.293 micron and 2.323 micron. Our results reveal a complex situation where the gas and stellar kinematics are totally unrelated. Supernova explosions play an important role in shaping the gas kinematics, dominated by shocks and inflows at scales of tens of parsecs that make them unsuitable to derive general dynamical properties. We propose that the location of the nucleus of M83 is unlikely to be related to the off-centre optical nucleus. The study of the stellar kinematics reveals that the optical nucleus is a gravitationally bound massive star cluster with M_dyn = (1.1 pm 0.4)x10^7 M_sun, formed by a past starburst. The kinematic and photometric analysis of the cluster yield that the stellar content of the cluster is well described by an intermediate age population of log T(yr) = 8.0pm0.4, with a mass of M simeq (7.8pm2.4)x10^6 M_sun.
