It would seem very logical: the more matter is available to a black hole, the more rapidly it can grow in size. However, there is a difference considering how that growth-fueling matter reaches its destination. Even though one could expect a linear dependency, the interactions between the streams of the infalling matter could enhance the black hole’s ingestion rate by more than 2-3 orders of magnitude. Quite an appetite boost, isn’t it?

A team of Italian scientists have published a research paper at arXiv.org. They simulated the supermassive black hole‘s behavior under the action of two distinct streams of gas forming a pair of separate accretion discs. The motivation for such modeling came from previous studies, which identified significant differences in black hole growth rates. It was also noted previously that larger black holes – like those hosted inside Active Galactic Nuclei (AGN) – require not only a large reservoir of gas, but even more importantly an efficient mechanism to transport gas from larger distances (up to 10 kpc) down to the range where an accretion disc can be formed and subsequently devoured by AGN.

The authors considered a potential trigger of black hole accretion on the galactic scale: the interaction between the nested and misaligned inflows of gas clouds and the resulting redistribution of their angular momenta.

The team performed a three-dimensional simulation of the interstellar gas hydrodynamics to determine the theoretical consequences of this assumption. According to the initial conditions, the modeled system contained three main components: a black hole itself, a primitive gaseous disc of size ~16 pc rotating around the central black hole in a stable configuration, plus a spherical shell gas cloud of size ~100 pc centered at the same point of rotation, gradually collapsing towards the central black hole due to the action of gravity.

The simulation showed some interesting results. It appeared, that the separate overlapping events of the surrounding gas inflow produce hydrodynamical shocks, which redistribute the trajectory of the matter spiralling inwards to the black hole. Simply put, the external gas flow makes a shortcut by crossing the boundary of the inner accretion disc, thus enhancing the overall inflow rate by more than 2-3 orders of magnitude.

The simulations were also performed without considering the interaction between separate inflow events: the presence of interaction resulted in a substantial and a non-linear increase of the black hole growth rate in all experiments. The authors of the study hope that their research will shed more light on the formation and evolution of supermassive black holes and how such processes influence the physical changes of central galactic regions.

By Alius Noreika, Source: www.technology.org