Stellar Winds Pump the Heart of the Milky Way

• Published in: Astrophysical journal. Letters Vol. 888; no. 1; p. L2
• Main Authors: Calderón, Diego, Cuadra, Jorge, Schartmann, Marc, Burkert, Andreas, Russell, Christopher M. P.
• Format: Journal Article
• Language: English
• Published: Austin The American Astronomical Society 01.01.2020; IOP Publishing
• Subjects: Accretion; Cold gas; Computer simulation; Deposition; Galactic center; Galactic nuclei; Hydrodynamics; Milky Way; Quasi-steady states; Stars; Stellar winds; Supermassive black holes
• ISSN: 2041-8205; 2041-8213
• DOI: 10.3847/2041-8213/ab5e81

The central supermassive black hole of the Milky Way, Sgr A*, accretes at a very low rate making it a very underluminous galactic nucleus. Despite the tens of Wolf-Rayet stars present within the inner parsec supplying ∼10−3 M yr−1 in stellar winds, only a negligible fraction of this material (<10−4) ends up being accreted onto Sgr A*. The recent discovery of cold gas (∼104 K) in its vicinity raised questions about how such material could settle in the hostile (∼107 K) environment near Sgr A*. In this work we show that the system of mass-losing stars blowing winds can naturally account for both the hot, inefficient accretion flow, as well as the formation of a cold disk-like structure. We run hydrodynamical simulations using the grid-based code Ramses starting as early in the past as possible to observe the state of the system at the present time. Our results show that the system reaches a quasi-steady state in about ∼500 yr with material being captured at a rate of ∼10−6 M yr−1 at scales of ∼10−4 pc, consistent with the observations and previous models. However, on longer timescales ( 3000 yr) the material accumulates close to the black hole in the form of a disk. Considering the duration of the Wolf-Rayet phase (∼105 yr), we conclude that this scenario has likely already happened, and could be responsible for the more active past of Sgr A*, and/or its current outflow. We argue that the hypothesis of the mass-losing stars being the main regulator of the activity of the black hole deserves further consideration.