An Active Galactic Nucleus (AGN) is a highly luminous region at the center of a galaxy, powered by the accretion into a supermassive black hole and emitting energy from radio waves to gamma rays,... Show moreAn Active Galactic Nucleus (AGN) is a highly luminous region at the center of a galaxy, powered by the accretion into a supermassive black hole and emitting energy from radio waves to gamma rays, often outshining the host galaxy. In the context of the AGN unification paradigm, the concept of the dusty “torus” plays a crucial role to discern between Type-1 and Type-2 AGNs depending on whether it obscures the AGN from the observer’s line of sight. NGC 1068, a well-studied AGN across the electromagnetic spectrum, is a nearby barred galaxy (d=14.4 Mpc) considered the prototypical Type-2. Using MATISSE at the VLTI, we have obtained direct evidence of the dusty torus enshrouding the AGN in NGC 1068. The multi-band capabilities of the instrument in the infrared wavelengths and the high spatial resolution that the interferometric technique can achieve have enabled us to study in detail the characteristics of the obscuring dust and its spatial distribution. We further analyse ALMA observations of the molecular gas with a comparable angular resolution. The revealed kinematics suggest an ongoing merger event, potentially contributing to the observed asymmetries in the torus and the water-maser disk, offering new insights into the dynamic processes in AGNs. Show less
Chemistry plays an important role in the study of the physics and evolution of the warm dense Interstellar Medium (ISM). This is found in very different environment, e.g. in the disks around low... Show moreChemistry plays an important role in the study of the physics and evolution of the warm dense Interstellar Medium (ISM). This is found in very different environment, e.g. in the disks around low-mass young stellar objects (YSOs), in the envelopes of massive-YSOs, and in the nuclei of Ultra Luminous Infrared Galaxies (ULIRGS). The excitation temperatures and abundances of the observed molecules provide the observer with a physicochemical snapshot of the regions. The abundances of the molecules depend strongly on temperature, density, radiation field (UV, Infrared, and X-ray) and initial composition of the gas. Infrared spectroscopy is instrumental in the study of dense ISM as many species have transitions in the infrared. Space based instruments, unhindered by the earth atmosphere, allow us to study these. The absorption and emission features are often weak. Therefore a major challenge in using these instruments is to understand the instrumental characteristics and translating that knowledge into usable reduction algorithms. Most of the data used in this thesis are obtained with space based spectrographs, ISO-SWS and Spitzer-IRS, pushing them to their limits. Show less
