NEAR-IR INTEGRAL FIELD SPECTROSCOPY STUDY OF THE STAR FORMATION AND AGN OF THE LIRG NGC 5135

We present a study of the central 2.3kpc of NGC5135, a nearby Luminous Infrared Galaxy (LIRG) with an AGN and circumnuclear starburst. Our main results are based on intermediate spectral resolution (� 3000-4000) near infrared data taken with the SINFONI integral field spectrograph at the ESO VLT. The ionization of the different phases of the interstellar gas and the complex structures of the star formation have been mapped. Individual regions of interest have been identified and studied in detail. For the first time in this galaxy, we have detected the presence of a high excitation ionization cone centered on the AGN by using the [SiVI]�1.96µm line. So far, this structure is the largest reported in the literature for this coronal line, extending (in projection) as far as � 600pc from the galaxy nucleus. In a complex spatial distribution, a variety of mechanisms are driving the gas ionization, including SNe remnant shocks, young stars and AGN photoionization. The excitation of the molecular gas, however, is mainly produced by X-rays and SNe remnant shocks. UV-mechanisms like fluorescence represent a marginal overall contribution to this process, contrary to the expectations we might have for a galaxy with a recent and strong star formation. Our SNe rate estimations from [FeII]�1.64µm are in excellent agreement with 6cm radio emission predictions. Typical SNe rates between 0.01-0.04yr −1 were found for individual � 200pc-scale regions, with an overall SNe rate of 0.4-0.5yr −1 . Even though NGC5135 has suffered a recent starburst (6-7Myr ago), the data strongly suggest the presence of a second, older stellar population dominated by red giant/supergiant stars. However, simple stellar population models cannot sharply discriminate between the different populations. Subject headings: galaxies: Seyfert - galaxies: nuclei - galaxies: structure - galaxies: ISM - infrared: galaxies - infrared: ISM - (ISM:) supernova remnants - galaxies: general