It is believed that in every galaxy there is a supermassive black hole located in the core. The active galaxy becomes if the hole is fed by matter and glows. This “central engine” is usually surrounded by pulverized molecular gas, which is shaped like a donut. He hides a black hole and stuff. It is commonly assumed that this kind of propagation applies to all accreting supermassive black holes, which explain the apparent diversity of active galaxies from the brightest quasars to low-light radio galaxies.
However, it is known that weak radio galaxies are endowed with characteristics incompatible with this model and having no evidence of bright accretion and “donut” shading structures. This leads to the idea that black holes or gas flows are unique. New data from the University of Manitoba show that about 1/3 of weak radio galaxies are endowed with luminous gas and black holes hidden by dusty donuts. All of them are viewed in the infrared range. To understand this, scientists conducted a correspondence to the IR spectrum of a sample of weak radio galaxies with several components, including gas, dust and a torus. It turned out that 1/3 radio galaxies demonstrate classical central engines with accretionary structures and donuts. There is an assumption that for weaker active galaxies, the properties of the central engine are rapidly changing. Usually, black holes in such galaxies are on a diet due to the lack of approximate material, but they are periodically fed. At such moments, much more mass falls into the black hole, which leads to the creation of a standard bright structure of accretion and shading of the torus.