Galactic 'Heart and Lungs' Mechanism Regulates Growth

A recent study published in the Monthly Notices of the Royal Astronomical Society proposes that galaxies possess a "heart and lungs" mechanism that regulates their growth and prevents them from becoming overly large. This finding sheds light on why galaxies are not as massive as previously anticipated.

The research, conducted by astrophysicists at the University of Kent, suggests that galaxies can control their growth rate through a process akin to breathing. The supermassive black hole at a galaxy's center functions as the heart, while the bi-polar supersonic jets of gas and radiation act as the airways feeding the lungs.

PhD student Carl Richards developed this theory using innovative simulations to explore the impact of supersonic jets on galaxy growth. These simulations showed that pulses from the black hole cause jet shock fronts to oscillate, similar to how the thoracic diaphragm moves in the human body, resulting in widespread energy transmission that slows gas accretion and galaxy growth.

Richards explained, "We realised that there would have to be some means for the jets to support the body - the galaxy's surrounding ambient gas - and that is what we discovered in our computer simulations." The simulations revealed that high-pressure jets, driven by pulsing black holes, act like bellows, sending sound waves through the galaxy's gas and creating pressure ripples that inhibit growth.

Professor Michael Smith, a co-author of the study, added, "Breathing too fast or too slow will not provide the life-giving tremors needed to maintain the galaxy medium and, at the same time, keep the heart supplied with fuel."

The researchers concluded that this "heart and lungs" mechanism helps sustain the galaxies we observe today. Without it, galaxies might have used up their fuel and collapsed into "red and dead" or "zombie" states.

Research Report:Simulations of Pulsed Overpressure Jets: Formation of Bellows and Ripples in Galactic Environments