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Near-IR Integral Field Spectroscopy Study of the Star Formation and AGN of the LIRG NGC 5135
We present a study of the central 2.3 kpc of NGC 5135, a nearbyluminous infrared galaxy (LIRG) with an active galactic nucleus (AGN)and circumnuclear starburst. Our main results are based on intermediatespectral resolution (~3000-4000) near-infrared data taken with theSINFONI integral field spectrograph at the ESO VLT. The ionization ofthe different phases of the interstellar gas and the complex structuresof the star formation have been mapped. Individual regions of interesthave been identified and studied in detail. For the first time in thisgalaxy, we have detected the presence of a high excitation ionizationcone centered on the AGN by using the [Si VI]λ1.96 μm line. Sofar, this structure is the largest reported in the literature for thiscoronal line, extending (in projection) as far as ~600 pc from thegalaxy nucleus. In a complex spatial distribution, a variety ofmechanisms are driving the gas ionization, including supernova remnant(SNR) shocks, young stars and AGN photoionization. The excitation of themolecular gas, however, is mainly produced by X-rays and SNR shocks. UVmechanisms like fluorescence represent a marginal overall contributionto this process, contrary to the expectations we might have for a galaxywith a recent and strong star formation. Our supernova (SN) rateestimations from [Fe II]λ1.64 μm are in excellent agreementwith 6 cm radio emission predictions. Typical SN rates between 0.01and 0.04 yr-1 were found for individual ≈200 pc-scale regions, with an overall SN rate of 0.4-0.5yr-1. Even though NGC 5135 has suffered a recentstarburst (6-7 Myr ago), the data strongly suggest the presence of asecond, older stellar population dominated by red giant/supergiantstars. However, simple stellar population models cannot sharplydiscriminate between the different populations.
| Five-colour photometry of early-type stars in the direction of galactic X-ray sources
The results of five-color (Walraven system) photometry of 551 O- andB-type stars located in 17 fields of a few square degrees aroundgalactic X-ray sources are presented. From a comparison ofreddening-free combinations of color indices with theoretical values,calculated for model atmospheres of Kurucz (1979), effective temperatureand surface gravity for these stars are derived. In addition theirabsolute magnitude are determined by combining these parameters with theresults of evolutionary calculations of massive stars. These effectivetemperatures are in good agreement with the temperature scale ofBohm-Vitense (1981) for stars of luminosity classes II to V. For thesupergiants the effective temperatures are about 40 percent higher. Forstars of luminosity classes III to V the absolute magnitudes agree wellwith the results of independent luminosity calibrations of spectraltypes, but for brighter stars they deviate systematically. Thephotometric data are also used to study the interstellar reddening inthe direction of the X-ray sources.
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