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Curated by RSF Research Staff

Nuclear activity of black holes

Gradually as the observing tools are improving, astronomers confirm the existence of black hole at the center of astronomical events. One of these is the active galactic nuclei. They have been a rich field of research since their discovery in the 1940s. These regions of space contain a super massive black hole in the range which converts the potential energy of matter in an accretion process to radiation and particle outflow.  Their dynamics raised a lot of questions like the spinning rate if their central black hole, the accretion mechanism, the dynamic of their jets. Intense observations of these areas of space could give us solid answers in a near future.

The region called active galactic nuclei is present in many galaxies. It is a very bright area that could be more luminous than the remaining galaxy light. Most of the energy output is under the form of X-rays, radio and ultraviolet radiation, as well as optical radiation. Directly studying these galactic nuclei will improve our knowledge about galaxy evolution.

Schematic representation of the unified AGN model. Various types of AGN can be understood as the result of different viewing angles, whether the central black hole is producing a jet, and the power level of the central source. [Beckmann & Shrader 2012]

Recently, a team lead by Cristina Ramos Almeida from the IAC (Instituto de Astrofísica de Canarias, Spain) has published new insight on the composition of the active galactic nuclei. They studied the material surrounding accreting supermassive black holes and its connection between the active galactic nucleus and its host galaxy. They looked closely to local active galactic nuclei carried out in the infrared and X-ray regimes. They found a complex structure divided in two parts: an equatorial disk/torus and a polar component. However, we still need more precision to deep into the detailed mechanisms.

"We now know that this nuclear material is more complex and dynamic than we thought a few years ago: It is very compact, formed by gas and dusty clouds orbiting the black hole, and its properties depend on the active galactic nucleus luminosity and accretion rate. Moreover, it is not an isolated structure, but appears connected with the galaxy via outflows and inflows of gas, like streams of material flowing as part of a cycle. This gas flow cycle keeps feeding the black hole and regulates the formation of new stars in the galaxy."

Cristina Ramos Almeida, researcher at the IAC

In the coming decade, the new generation of infrared and X-ray facilities will greatly contribute to a better understanding of these structures.

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