L'impatto dell'attività AGN sul mezzo interstellare della galassia ospite

In this Thesis I investigate how, and to which extent, Active Galactic Nuclei (AGN) activity affects the properties of the host-galaxy interstellar medium (ISM). AGN are thought to regulate the host star formation (SF) by injecting large amount of energy in the circumnuclear region, either suppressing or enhancing the formation of new stars. To understand the interplay between AGN and SF multi-wavelength approach is needed, which allows us to trace the different gas components. In the first part of the Thesis, I present the result of a systematic analysis of the X-ray properties of a sample of local Seyfert 2 galaxies (Gruppioni et al. 2016), necessary to characterise the AGN activity to unveil its intrinsic power. To investigate the properties of the dusty torus in different bands, I compare the level of obscuration estimated from the X-ray spectral analysis, with the one derived from the strength of the 9.7μm silicate feature in the mid-IR. In the second part of the Thesis, I determine the molecular gas content of the same sample of Seyfert 2 galaxies by using single-dish observations tracing the CO emission line. By comparing our results with a control sample of inactive galaxies, I observe that AGN do not differentiate from star-forming galaxies (SFGs) in terms of molecular gas content and corresponding depletion time. I also assess the influence of AGN on the emission of SF tracers in the mid-IR features. Finally, I provide a complete and coherent multi-wavelength characterisation on a test case galaxy, NGC 7213, drawn from the same parent sample. This target came out to be of particular interest because of the kinematical modelling on ALMA data, which reveals the presence of two molecular outflows. I complement the analysis with a detailed X-ray spectral analysis to determine the AGN accretion power.