If the universe were to age faster than it is now, we would find it filled with “zombie galaxies” full of dead stars. But since that’s not the case, some kind of self-preservation mechanism must be in place. Scientists from Great Britain compared this to the “heart” and “lung” that regulate the “breathing” and growth of galaxies.

Most spiral galaxies have star-forming regions. Their main building material is hydrogen gas with a small amount of heavy elements. The first galaxies in the universe had huge reserves of “fuel”, which, according to theory, should have been used up quickly. The explosion of star formation will not last long, and the galaxies will quickly disappear, but they seem to be able to delay their death thanks to the supermassive black holes located at their cores.

Galaxies evolve under the influence of the interaction between the interstellar medium and the surrounding gaseous halo known as the circumgalactic medium.Galactic environmentThe halo, although significantly less dense than the interstellar medium, contains three to five times more baryons and heavy elements. However, estimates of star formation rates in many galaxies are lower than expected.

Scientists explain this paradox by the fact that relativistic jets (two multi-directional plasma jets coming from active galactic nuclei) can heat the intergalactic medium and soften the flows. To find out, scientists from the University of Kent (Great Britain) studied the shock structure of the jets using axisymmetric hydrodynamic models at M = 2 (Mach number). In a new study published Monthly Notices of the Royal Astronomical Society Researchers have developed models and provided explanations for some of the observed phenomena.

The authors of the paper compared the black hole at the center of the galaxy to the heart, and the jets to the air that enters the respiratory tract and fills the lungs. During exhalation, abnormally high pressure areas appear in the jet, creating shock waves. Just as the diaphragm rises and falls, its front sections move back and forth along both axes, filling the lungs with air.

Continuing the analogy, just as our breath warms cold air, jet shock waves transfer their energy to the surrounding medium, making it warmer. This slows down the cooling and accretion of the circumgalactic medium.

The idea belongs to graduate student Carl Richards, first author of the paper, who used simulations to investigate the role of supersonic flows in slowing down the growth of galaxies. The scientist created a simulation of the pulsation of a black hole and the formation of abnormal pressure zones in the jets, similar to those in hypertension in humans. According to Richards, the jets work like blacksmith’s fur, producing sound waves like ripples on the surface of a pond. This could explain the observation of fluctuations in the galactic clusters Perseus and Centauri.

According to scientists, the processes occurring in jets with abnormally high pressure zones can be compared to the sound of opening a bottle of champagne or piercing an inflated bag. In general, the model explains why the flow of cold gas from the halo is restricted. Now it is necessary to study in more detail the degree and efficiency of energy transfer, the possibility of overheating, and to make calculations with a large value of the Mach number, which, according to the authors, is of critical importance. model.