by Andreas Burkert
We investigate the origin, structure and evolution of the small gas cloud, G2, which is on an orbit almost straight into the Galactic central supermassive black hole (Gillessen et al., 2012). The movie shows the evolution of the cloud in an idealised hot atmosphere, using the hydrodynamics code PLUTO. With the help of such simulations and analytical calculations, we find that G2 is a sensitive probe of the hot accretion zone of Sgr A* and we can show that the observed structure and evolution of G2 can be well reproduced if it formed in pressure equilibrium with the surrounding in 1995 at a distance from the SMBH of 7.6e16 cm. Another possibility is that G2 is the head of a larger, shell-like structure that formed at apocenter. Our numerical simulations show that this scenario explains not only G2's observed kinematical and geometrical properties but also the observations of a low surface brightness gas tail that trails the cloud. In 2013, while passing the SMBH G2 will break up into a string of droplets that within the next 30 years mix with the surrounding hot gas and trigger cycles of AGN activity.
Click on the image to see the ESO press release movie (Credit: ESO/MPE/M.Schartmann/L.Calçada)!