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Bars are large triaxial structures in the centers of galaxy disks, having sizes varying from a few 100 pc to several kpc. Nearly 2/3rd of all disk galaxies in our local universe are barred. Bars play a crucial role in galaxy formation, shaping the structure of a galaxy’s dark matter halo, bulge, and disk and influencing its star formation history. Despite decades of research, the mechanism of bar formation in galaxies is still a subject of debate. From isolated galaxy simulations we have gained valuable insight to how bars form and evolve. However, bars in the Universe evolve in galaxies in highly complex environments with multiple satellite interactions, mergers, gas accretion events, star-formation and gas in-fall to the central supermassive blackhole (SMBH), while simultaneously interacting with their dark matter halo. Investigating bar formation and reproducing their observed properties in cosmological simulations is important for understanding galaxy formation, as well as understanding the formation of galactic bars. In this talk, I will present our work with the zoomed-in cosmo-hydro simulation FIRE-2 (Feedback in Realistic Environments). We study 13 high resolution MW-mass galaxies from FIRE2 to first ask: Do the FIRE galaxies have bars? If so, how do bars form and when does bar formation fail? We find examples where bars form due to satellite interactions and others where bars form secularly in the disk. The stellar feedback prescription in FIRE2, which affects starburst and gas dynamics, and the lack of blackhole feedback to mitigate the gas in the galaxy center, together make the disk kinematically hot, such that bars are shorter than the MW-bar, rotate faster, and are mostly short-lived. Using predictions from controlled simulations for varied dark matter and stellar distributions at the galaxy center, we explain the morphological differences between the bars in FIRE2 and TNG50 and connect them to differences in the physics implementations of the two codes. In addition to known influences on bar formation such as mergers and the mass ratio of stellar to dark matter in the inner galaxy, we argue that the burstiness of stellar feedback plays a crucial role in bar formation. In the end, I will touch upon some other works I have been involved with, to study the dark matter halo properties using the baryonic disk properties using N-body and cosmological simulations. |
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