Astrophysicist Matas Tartėnas from FTMC Department of Fundamental Research has earned his PhD in natural sciences. On March 28, he successfully defended his dissertation "Supermassive Black Hole Feeding and Feedback." His academic supervisor was Dr Kastytis Zubovas.
We congratulate our colleague and wish him continued success in exploring the mysteries of the Universe!
The scientist provides a detailed explanation of his dissertation:
"Observations over the past decades have revealed that almost every massive galaxy harbours a supermassive black hole at its center. From the name alone, one might assume that these exotic objects dominate, and galaxies revolve around them, but this is certainly not the case. The gravitational influence of supermassive black holes is dominant only within a relatively small region around them, and their feeding [the process in which a black hole absorbs material from its surroundings] - is governed by phenomena occurring beyond their sphere of influence.
The inflow of material - interstellar gas - towards central black holes is a rather complex and not yet fully resolved problem. My dissertation examines precisely this issue: how the feeding of central supermassive black holes occurs and what effects the resulting outflows and winds have on galaxies.
(The first direct image of a supermassive black hole, found in the galactic core of Messier 87. Photo: Wikipedia.org)
The centers of galaxies are highly dynamic systems, making numerical hydrodynamic models essential for their study. Using such models, we can create strictly controlled conditions and determine the dominant processes in various scenarios. Moreover, since we have (virtually) complete information about the simulated system, it is easier to identify new phenomena or predict aspects that warrant attention when directing telescopes towards a target in the future.
Modern telescopes, such as the James Webb Space Telescope, ALMA, and the Event Horizon Telescope [which captured the first-ever image of a black hole], allow us to observe the Universe in unprecedented detail. New data, particularly regarding active galactic nuclei in the early Universe, compel us to reconsider even well-established assumptions about black hole feeding and their role in galaxy and cosmic evolution.
In this dynamic scientific landscape, even relatively simple numerical models - which do not encompass an entire galaxy, let alone vast clusters - find their place and are incredibly useful. They assist in calibrating larger simulations and answering specific questions that large-scale models (at least for now) cannot. For instance, "Can supermassive black hole winds trigger star formation?" or "How do gas clouds overcome the final few parsecs before being consumed by the black hole?"
(The Galactic Center of the Milky Way seen from Earth's night sky (featuring the telescope's laser guide star). Photo: Wikipedia.org)
Our research explored a possible activity scenario for the Milky Way. Using a relatively simple model, we demonstrated that the circumnuclear ring observed in the galaxy's center plays a crucial role in explaining intermittent episodes of activity. Such structures naturally form and grow due to isolated collisions until a rarer counter-collision allows a significant portion of this reservoir to feed the black hole. Similar structures are observed in other galaxies, suggesting that this scenario may not be unique to the Milky Way.
Our models also showed that even during periods of intense activity, powerful outflows do not necessarily destroy the densest structures, such as central rings or clouds. This finding helps explain the formation of stars in the center of the Milky Way during an activity episode approximately six million years ago. More broadly, it supports the hypothesis that black hole feedback can, in certain cases, enhance – albeit temporarily – star formation," explains M. Tartėnas.
Info: FTMC