Feeding and Feedback in the central parsec of the Milky Way

Sgr A*, a peculiar radio source in the centre of the Galaxy, also detected in X rays and near infra red, is the closest to us and the best studied supermassive black hole. These objects are very important for Galaxy formation and evolution but are far from being completely understood1.
Sgr A* is a unique test bed for theories of supermassive black hole evolution. It is fairly well established now that the central parsec of our Galaxy hosted a powerful starburst about 6 million years ago2 and that Sgr A* accreted a fair fraction of that gas4, producing powerful outflows, inflating the gamma ray emitting bubbles called the Fermi Bubbles3. The young stars orbiting Sgr A* provide us with constraints on the mass and orbital configuration of the gas that fed Sgr A* six million years ago4.

However, a detailed understanding of how the disc was created, how and which fraction of it was converted into stars, how Sgr A* feedback was produced and how the outflow interacted with the disc and the larger scale environment5 is still lacking. With new data7, it is now possible to test scenarios of Sgr A* feeding, feedback, and star formation combined to yield the stellar configuration observed now8.

This project will aim to expand our knowledge of how the events unfolded in the Galactic Centre, and in doing so also aim to shed light on the workings of the inner parsecs of all galaxies in general. Sgr A* stellar orbital constrains will also be invaluable in constraining how AGN feedback outflows interact with the clumpy and highly variable environment of the central regions of galaxies9.

The project will be theoretical in nature but will be well linked with observational constraints via collaboration with Galactic Centre observers.

During the first year, two topics are to be addressed.

1 - Previous work considered how turbulent gas clouds or shells are deposited in the central parsecs and feed the blackhole4,10 and, separately, how such shells are blasted by the feedback outflows9. However, how these two processes would operate simultaneously in a single source has not so far been studied. The candidate will use the existing numerical codes 5, 9, 10 to address this issue in a set of simulations to understand the problem in general. Do AGN outflows prevent or change the nature of chaotic gas inflows that were suggested to feed the blackholes?
2 - This study will then be further tailored to trying to reproduce the data including,
(a) the stellar orbits and the unusual mass spectrum in the central parsec,
(b) the structure of the circum nuclear disc on the scales of a few parsec;
(c) the central molecular zone on the scale of 100 pc which may have shaped Sgr A* outflow3,5 into
(d) the Fermi Bubbles.
The candidate will use initial conditions similar to those of previous studies (e.g., refs 4 and 10) and include powerful outflows to understand how these change theoretical predictions for the observables (a to d)