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Abstract

The rapid suppression of star formation, or quenching, is thought to be an important process in the evolution of the most massive galaxies, but the mechanisms involved are still hotly debated. Here, we consider two agents that control star formation and can ultimately lead to its suppression: AGN feedback and galaxy mergers.

In the first part of the thesis, we study the interplay between stellar structure, nuclear activity, and molecular gas in the context of AGN feeding and feedback. We start presenting our catalogue of stellar mass maps for more than 1500 nearby galaxies, which has been publicly released. Using the stellar mass map of the spiral galaxy M51, we show that there is sufficient molecular gas inflow to feed the AGN (~1 Msun/yr), and feedback effects which include a nuclear molecular outflow (at a rate comparable to the inflow), as well as a large-scale radio jet which pushes molecular gas laterally, inducing shocks and turbulence.

In the second part, we address the role of galaxy mergers in the buildup of a passive population of lenticular galaxies (or S0s). While lenticulars are the most common early-type galaxies in the Universe, their formation channels remain elusive. We use numerical simulations to show that even major mergers of spiral galaxies can result in lenticulars, with a bulge-disc coupling in agreement with observations. We also find that major mergers can simultaneously account for the difference in angular momentum and concentration between spirals and S0s, as recently found by the CALIFA team.

Globally, our results show that both internal processes (transport of gas and AGN feedback) and external mechanisms (mergers) have the ability to regulate and eventually suppress star formation in galaxies. Current and future instrumental advancements (ALMA, NOEMA, JWST) will permit to confirm our findings with other galaxies and further assess their relative importance.