Observational evidence s suggest a co-evolution of the central supermassive black holes and their host galaxies. In some of them, the black hole is ingesting the material surrounding it at a very high rate, emitting a large quantity of energy. In those cases we say that the galaxy has an active nucleus (AGN). Studying the mechanisms which control the relation between the active nucleus and the rest of the galaxy is essential to understand how these objects form and evolve, and to be able to throw light on this question we need to compare active and non-active galaxies. Here, we first identif

Some galaxies in the Universe display beautiful and appealing features known as "spiral arms". However, not all galaxies show spiral arms in the same manner. Among the variety of cases the Large Magellanic Cloud (LMC), a dwarf galaxy infalling towards the Milky Way, stands out. The LMC is the prototype of an entire family of galaxies, the Magellanic Spirals that are characterised by the presence of a barred stellar structure near their centres and a single spiral arm. Spiral patterns can form after galactic collisions, with subsequent star formation piling up in these arms. Nevertheless, we

The long-standing difference in chemical abundances determined from optical recombination lines and collisionally excited lines raises questions about our understanding of atomic physics, as well as the assumptions made when determining physical conditions and chemical abundances in astrophysical nebulae. Here, we study the recombination contribution of [O III] 4363 and the validity of the line ratio [O III] 4363/4959 as a temperature diagnostic in planetary nebulae with a high abundance discrepancy. We derive a fit for the recombination coefficient of [O III] 4363 that takes into account