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Black hole “donuts” are actually “fountains”

ALMA image of the gas around the super massive black hole in the middle of the Circinus Galaxy. The distribution…

ALMA image of the gas around the super massive black hole in the middle of the Circinus Galaxy. The distribution of CO molecular gas and C-atom gas is shown in orange and cyan respectively. Credit: ALMA (ESO / NAOJ / NRAO), Izumi and others.

Researchers, based on computer simulations and new observations from Atacama Large Millimeter / submillimeter Array (ALMA), found that the gas rings around active super massive black holes are not simple donuts. Instead, gas exchanges from the center with incident gas to create a dynamic circulation pattern resembling a water fountain in a city park.

Most galaxies host a super massive black hole, millions or billions of times as heavy as the sun, in their centers. Some of these black holes swallow the material quite actively. But astronomers have thought that instead of falling directly into the black hole, matter instead will be built around the active black hole that forms a monk structure.

Takuma Izumi, a researcher at Japan’s National Astronomical Observatory (NAOJ) led a team of astronauts who used ALMA to observe the super massive black hole in Circinus Galaxy, which lies 1

4 million light years away from the Earth in the direction of the Circulus constellation. The team then compared their observations with a computer simulation of gas falling against a black hole made by the Cray XC30 ATERUI supercomputer powered by NAOJ. This comparison showed that the presumptive “donut” is not a rigid structure, but instead a complex combination of high-dynamic gaseous components. First of all, cold molecular gas falling against the black hole forms a disc near the rotational plane. As it approaches the black hole, this gas is heated until the molecules break down into component atoms and ions. Some of these atoms are then expanded over and under the counter, instead of being absorbed by the black hole. This hot atomic gas falls back onto the disc and creates a turbulent three-dimensional structure. These three components circulate continuously, resembling a water fountain in a city park.

The artist’s impression of gas movement around the super massive black hole in the middle of the Circinus Galaxy. The three gaseous components form the long-theorized “nozzle structure”: (1) a disc of incident dense cold molecular gas, (2) exhaust hot atom gas and (3) gas returning to the disk. Credit: NAOJ

“Previous theoretical models established previous assumptions about stupid monks,” explains Keiichi Wada, a theorist at Kagoshima University in Japan, who heads the simulation study and is a member of the research group. “Instead of starting with assumptions, our simulation started from the physical equations and showed for the first time that gas circulation naturally forms a monk. Our simulation can also explain different observation characteristics of the system.”

“By examining the motion and distribution of both the cold molecular gas and the hot nuclear energy with ALMA, we showed the rise of the so-called” donut structure “around active black holes,” said Izumi. “Based on this discovery, we have to write about the astronomy books.”

Cross section of the gas around a super massive black hole simulated with NAOJ supercomputer ATERUI. The different colors represent the density of the gas, and the arrows show the movement of the gas. It clearly shows the three gaseous components that form the “donut structure”. Credit: Wada et al.

Explore further:
Rotating gaseous monk around an active super massive black hole

More information:
Takuma Izumi et al. Circumnuclear Multiphase Gas in Circinus Galaxy. II. The molecular and atomic obscuring structures revealed by ALMA, Astrophysical Journal (2018). DOI: 10.3847 / 1538-4357 / aae20b

Journal Reference:
Astrophysical journal

Provided by:
National Astronomical Observatory of Japan

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