Abstract:
In May 2022, the Event Horizon Telescope has revealed the first image of Sgr A*, the supermassive black hole at the center of our Milky Way Galaxy. Understanding the past activity of Sgr A* has been one of the key questions to address as it will allow us to gain insights into the formation history of the Milky Way. One of the most prominent signature for possible past activity of Sgr A* is the Fermi bubbles, two giant gamma-ray bubbles discovered in 2010. The origin of the Fermi bubbles has been intensely debated; however, in 2020 the newly launched eRosita X-ray satellite has revealed another pair of "eRosita bubbles", providing new constraints on their formation mechanisms. The enormous sizes, symmetries, and properties of the Fermi/eRosita bubbles strongly suggest that they share the same origin. Using cutting-edge numerical simulations including cosmic-ray physics, we show that the Fermi/eRosita bubbles likely originate from past jet activity of Sgr A* about 2.6 million years ago.