We study the central regions of galaxies, including the center of the Milky Way. We are interested in the activity of supermassive black holes, how they grow, and how they interact with their surroundings. We investigate how the growth of supermassive black holes is influenced by their environment across different spatial scales and, conversely, how these black holes affect their surroundings. We use multi-wavelength observations in combination with theoretical and computational models.

It is now established that most galaxies host at least one supermassive black hole in their centers. Although these massive compact objects with masses of the order of million to billion Solar masses dynamically influence only tiny volumes around them with radii ranging from 0.5 parsec to 100 parsecs, via intense radiation and powerful outflows they can affect star-formation rates and cold gas content within their host galaxies and even beyond on galaxy cluster scales. It is therefore crucial to study black-hole growth processes such as accretion and mergers and how they affect galaxy evolution in the cosmological context.

We are studying motion of stars and gas distribution in the vicinity of the supermassive black hole in the center of the Milky Way, which is associated with the compact and variable radio source Sgr A*. We have searched for stars that orbit very close to Sgr A*. One of the record stars is S4716 that orbits Sgr A* on the scale comparable to the Solar System and one orbit takes only 4 years. One of the mysteries is how these relatively young stars could have formed so close to the supermassive black hole. A potentially key could be provided by still mysterious dust-enshrouded objects that are located similarly close to Sgr A* and exhibit signatures of young stellar objects. On the other hand, a recent detection of the binary star D9 orbiting the supermassive black hole, which is one of the dust-enshrouded objects (G objects), opens the possibility that these mysterious objects are products of the ongoing binary-star interactions and mergers. 

We have also been studying the interaction of stars and compact remnants with the accretion flow and nuclear outflows and jets around supermassive black holes. In this regard, we focus on how these smaller perturbing bodies can affect the accretion rate and outflows and if these collisions can significantly affect stellar evolution and the appearance of stars close to the supermassive black hole. To this goal, we performed detailed 3D hydrodynamic simulations of red giant collisions with the nuclear jet, which could have been present during the past enhanced activities of Sgr A*.

Another pressing question concerns the relation between merger-free processes (observed through galaxy morphology) and supermassive black hole feeding and feedback. In particular, members of our group are investigating the trend of strongly barred galaxies hosting a higher fraction of active galactic nuclei as well as other complex relations between galactic bars, bulges, and the activity of supermassive black holes.

Furthermore, we are also interested in the fundamental physics of gravitational theories and black holes, in particular the possibility to test the presence of charged black holes in the Universe and how to use accreting black holes to constrain cosmological models.

Financial Support

To conduct the research projects outlined above, we have received support from the Czech Science Foundation grants: Junior Star grant (GM24-10599M) and Czech-Polish collaboration grant (GF23-04053L).