Mon. Not. R. Astron. Soc.

The interplay between a galactic bar and a supermassive black hole: Nuclear fuelling in a subparsec resolution galaxy simulation

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We study the connection between the large-scale dynamics and the gas fuelling towards a central black hole via the analysis of a Milky Way-like simulation at subparsec resolution. This allows us to follow a set of processes at various scales (e.g. the triggering of inward gas motion towards inner resonances via the large-scale bar, the connection to the central black hole via minispirals) in a self-consistent manner. This simulation provides further insights on the role of shear for the inhibition of star formation within the bar in regions with significant amount of gas. We also witness the decoupling of the central gas and nuclear cluster from the large-scale disc, via interactions with the black hole. This break of symmetry in the mass distribution triggers the formation of gas clumps organized in a time-varying 250 pc ring-like structure, the black hole being offset by about 70 pc from its centre. Some clumps form stars, while most get disrupted or merge. Supernovae feedback further create bubbles and filaments, some of the gas being expelled to 100 pc or higher above the galaxy plane. This helps remove angular momentum from the gas, which gets closer to the central dark mass. Part of the gas raining down is being accreted, forming a 10 pc polar disc-like structure around the black hole, leading to an episode of star formation. This gives rise to multiple stellar populations with significantly different angular momentum vectors, and may lead to a natural intermittence in the fuelling of the black hole.