Formation of young boxy-peanut bulges in ringed barred galaxies - Astrophysics > Astrophysics of GalaxiesReportar como inadecuado

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Abstract: We investigate whether the formation mechanism of boxy and peanut-shapedB-PS bulges could depend on the gas content of the galaxy. We have performedN-body simulations with and without a gaseous component. In the second casestar formation-feedback recipes have also been implemented to create newstellar populations. As in many previous studies, in our N-body collisionlesssimulation, the B-PS is due to the classical break in the z mirror symmetrylasting roughly 200 Myr. When a gaseous component and star formation recipesare added to the simulation, the bulge-growing mechanism is quite different.The young stellar population that is born in the thin gaseous disc rapidlypopulates vertical resonant orbits triggered by the combined effects of thelinear horizontal and vertical ILRs. This leads to a B-PS bulge mainly made ofstellar material younger than the surrounding population. The non-linearanalysis of the orbital structure shows that the main orbit family responsiblefor the B-PS is not the same in the two cases. The 2:2:1 orbits prevail in thecollisionless simulation whereas additional asymmetrical families contribute tothe B-PS if a dissipative component is present and can form new stars. We foundthat 2:3:1 and 2:5:1 orbits trap a significant fraction of the mass. A flatringed discy stellar component also appears simultaneously with the thickeningof the young population. It is due to the star formation in a nuclear gaseousdisc located in the central kpc, inside the ILR, and accumulated there by thetorques exerted by the large-scale bar. Remarkably, it remains flat throughoutthe simulation although it develops a nuclear bar, leading to a double-barredgalaxy. We predict that two populations of B-PS bulges could exist and evencoexist in the same galaxy.

Autor: Herve Wozniak CRAL, Leo Michel-Dansac IATE



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