Date:
Tue, 09/02/201012:30-13:30
Location:
Kaplun Bldg, seminar room, 2nd floor
The effects of gas in galaxy mergers
Within the CDM paradigm, major and minor mergers are a generic feature of structure assembly in the hierarchical picture, and are now widely believed to be responsible for shaping many galaxy properties. Major mergers play an important role in transforming disc-dominated spiral galaxies into spheroids and triggering episodes of enhanced star formation, while minor mergers may explain the origin of thick discs and the diffuse stellar halo around galaxies.
Some recent studies have questioned whether thin, dynamically fragile discs such as the one observed in the Milky Way can survive the constant bombardment by incoming satellites. I will show that in dissipationless simulations minor mergers (1:10) cause the scale height of the disc to increase by up to a factor of two. When the presence of gas in the disc is taken into account this thickening is reduced by 25% (50%) for an initial disc gas fraction of 20% (40%). Final disc scale heights found in the simulations are in good agreement with studies of the vertical structure of spiral galaxies.
Similarly, it has been shown that the morphology of major merger remnants depends on the initial gas fraction. While dissipationless simulations lead to slow rotators, if cold gas is included in the initial discs (~40%), fast rotators can be created (depending on the merger orbit). I will show that when a hot gas halo is included in the simulations, fast rotators can be created, even for low initial cold gas fractions and independent of orbit. Finally, I will demonstrate how the star burst efficiency changes when a hot halo is included.
Within the CDM paradigm, major and minor mergers are a generic feature of structure assembly in the hierarchical picture, and are now widely believed to be responsible for shaping many galaxy properties. Major mergers play an important role in transforming disc-dominated spiral galaxies into spheroids and triggering episodes of enhanced star formation, while minor mergers may explain the origin of thick discs and the diffuse stellar halo around galaxies.
Some recent studies have questioned whether thin, dynamically fragile discs such as the one observed in the Milky Way can survive the constant bombardment by incoming satellites. I will show that in dissipationless simulations minor mergers (1:10) cause the scale height of the disc to increase by up to a factor of two. When the presence of gas in the disc is taken into account this thickening is reduced by 25% (50%) for an initial disc gas fraction of 20% (40%). Final disc scale heights found in the simulations are in good agreement with studies of the vertical structure of spiral galaxies.
Similarly, it has been shown that the morphology of major merger remnants depends on the initial gas fraction. While dissipationless simulations lead to slow rotators, if cold gas is included in the initial discs (~40%), fast rotators can be created (depending on the merger orbit). I will show that when a hot gas halo is included in the simulations, fast rotators can be created, even for low initial cold gas fractions and independent of orbit. Finally, I will demonstrate how the star burst efficiency changes when a hot halo is included.