Formation and Evolution of Barred Galaxies

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A large fraction of spiral galaxies contain bars. The presence of a bar can greatly affect the evolution of the host galaxy. The bar channels gas into the center of galaxies, where it is converted into stars. The nuclear reactions in these stars produce heavy elements (called "metals"), that are then ejected into the gas when the stars explode in supernovae. Also, if there is a supermassive black hole in the center of the galaxy, the gas flowing along the bar might fall onto the black hole, producing an active galactic nuclei (or AGN). We would therefore expect barred galaxies to have higher central star formation rates (SFR), higher central metallicity, and more intense AGN activity than unbarred galaxies. However, recent observations reveal a more complex picture. Only galaxies with strong bars show enhanced central star formation, and not all of them do: There appears to be significant differences between massive barred galaxies (stellar masses larger than 10-30 billion solar masses) and low-mass ones. All barred galaxies show an enhancement in central metallicity, but low-mass barred galaxies do not show a corresponding enhancement in central star formation. Some high-mass barred galaxies do, but not all of them. Instead, some massive galaxies with strong bars show a suppression of central star formation. This suggests that bars might, under some circumstances, quench star formation in the central regions, instead of boosting it. Also, we observe an anti-correlation between star formation and AGN activity in the center of barred galaxies. These observations reveal that galaxies of different masses, or with bars of different strength, can have drastically different star formation histories. To fully understand the evolution of these galaxies, we need to understand the interplay between the various physical processes driving this evolution. We propose to pursue a long-term project to study the evolution of barred galaxies. We will perform a series of numerical simulations of galaxy evolution. Our goal is to understand the physical processes that determine the history of star formation and metallicity in barred galaxies, and determine the role played by feedback in quenching star formation in some barred galaxies.