New simulations of the jets produced by rotating supermassive black holes in the cores of galaxies show how, with enough power, the corkscrewing fields (white squiggles) can force their way through surrounding gas and drill out of the galaxy, channeling hot gas into the interstellar medium (top). Less powerful jets get stalled inside the galaxy, however, their magnetic fields breaking and dumping hot gas inside and heating up the galaxy. These stalled jets may be part of the black hole feedback mechanism that periodically halts the inflow of gas that feeds the black hole. Simulations by Alexander Tchekhovskoy, a NASA Einstein postdoctoral fellow at UC Berkeley, and Omer Bromberg, a former Lyman Spitzer Jr. postdoctoral fellow at Princeton University who is now at Hebrew University in Jerusalem. _____________ UC Berkeley scientists have created a simulation of the powerful jets generated by supermassive black holes at the centers of the largest galaxies, explaining why some burst forth as bright beacons visible across the universe, while others fall apart and never pierce the halo of the galaxy. About 10 percent of all galaxies with active nuclei – all presumed to have supermassive black holes within the central bulge – are observed to have jets of gas spurting in opposite directions from the core. The hot ionized gas is propelled by the twisting magnetic fields of the rotating black hole, which can be as large as several billion suns. A 40-year- old puzzle was why some jets are hefty and punch out of the galaxy into intergalactic space, while others are narrow and often fizzle out before reaching the edge of the galaxy. The answer could shed light on how galaxies and their central black holes evolve, since aborted jets are thought to roil the galaxy and slow star formation, while also slowing the infall of gas that has been feeding the voracious black hole. The model could also help astronomers understand other types of jets, such as those produced by individual stars and we see as gamma-ray bursts or pulsars. “Whereas it was rather easy to reproduce the stable jets in simulations, it turned out to be an extreme challenge to explain what causes the jets to fall apart,” said University of California, Berkeley theoretical astrophysicist Alexander Tchekhovskoy, a NASA Einstein postdoctoral fellow who led the project. “To explain why some jets are unstable, researchers had to resort to explanations such as red giant stars in the jets' path loading the jets with too much gas and making them heavy and unstable so that the jets fall apart. ...

Physics 7B, 001 - Fall 2014 Physics for Scientists and Engineers - Achilles Speliotopoulos Creative Commons 3.0: Attribution-NonCommercial-NoDerivs