An international team of researchers, including dr Krzysztof Hryniewicz of the National Centre for Nuclear Research, has developed a new model describing the hot gas surrounding the supermassive black hole in the active galaxy Mrk 509. The findings help to better understand the structure of matter in the vicinity of active galactic nuclei.

The results were published in the prestigious journal Astronomy & Astrophysics (Volume 705, Article A119, https://doi.org/10.1051/0004-6361/202554950

A group of scientists consisting of Krzysztof Hryniewicz – National Centre for Nuclear Research, Agata Różańska, Biswaraj Palit, and Rafał Wojaczyński – Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences, Tek Prasad Adhikari – Hefei University of Science and Technology, and Matteo Guainazzi – European Space Agency (ESA), has undertaken research on active galaxies. These are galaxies in which a central supermassive black hole absorbs enormous amounts of matter. The flow of infalling matter takes the shape of a disk through which plasma flows at a rate of about the mass of the Sun per year. During this process, some of the gas does not fall into the black hole but is ejected from the disk into space in the form of a radiation-driven wind. Astronomers call such matter streams observed in the X-ray range “warm absorbers.”

These powerful gas outflows can influence the evolution of entire galaxies — regulating the rate of star formation and distributing energy and matter throughout interstellar space. Understanding their structure and behavior is one of the major challenges in modern astrophysics.

Scientists analyzed data from the XMM-Newton space X-ray telescope regarding the galaxy Mrk 509, located hundreds of millions of light-years from Earth. They utilized an unprecedented observation duration of as much as 900,000 seconds (over 10 days). This yielded high-resolution spectra, which allowed for a very precise study of the composition and structure of the gas surrounding the black hole.

– The aim of this work was to develop a more realistic model describing the behavior of hot gas around an active galaxy and to use it to explain high-quality observations. Until now, it was often assumed that gas clouds ejected from the accretion disk have a uniform density or consist of layers of constant density. We proposed a more physical approach — the constant total pressure (CTP) model — in which the density varies in a complex manner along the gas cloud. This is the result of both the gas pressure and the pressure caused by intense radiation emanating from the hot matter in the immediate vicinity of the black hole. This allowed us to better reproduce the observed X-ray spectrum, i.e., the characteristic “fingerprint” of the gas visible in the telescope data. The spectrum contains absorption lines — traces left by various chemical elements present in the hot gas along the line of sight. Analyzing them allows us to determine the temperature, density, chemical composition, and velocity of the matter moving around the black hole — explains dr Krzysztof Hryniewicz.

The researchers demonstrated that the gas responsible for absorbing most of the X-ray light in Mrk 509 is located at the center of the galaxy — about 0.02 parsecs from the black hole, a distance comparable to the inner regions of the accretion disk from which the black hole draws matter. The contribution of scientists from the National Centre for Nuclear Research (NCBJ) included modeling the processes occurring in the hot gas, analyzing X-ray data, and interpreting the physical properties of outflows of matter from the accretion disk.

This study addresses an important scientific issue concerning the impact of supermassive black holes on their surroundings. Although black holes are primarily associated with the absorption of matter, they can also influence entire galaxies through energy emissions and gas outflows. Research of this kind helps us better understand how galaxies have evolved over billions of years and how conditions favourable to the formation of stars and planets arose.

The significance of this work also extends beyond astronomy itself. The advanced computer models and data analysis methods developed in such projects are later applied in fields such as plasma physics, big data analysis, and the modeling of complex physical processes. The authors emphasize that the new model could help in more precise studies of active galaxies observed by future space telescopes and better explain the mechanisms governing the most energetic objects in the Universe.