GREEDY black holes may suffocate their host galaxies by hogging the gas needed to make stars.
There are two main types of galaxies: 鈥渂lue鈥�, star-forming galaxies and 鈥渞ed and dead鈥� galaxies that no longer form new stars. Blue galaxies seem to evolve into red ones, but nobody is sure how or why. Simulations now suggest black holes at the centres of galaxies may be the cause.
The biggest galaxies are also the most stagnant. Once galaxies reach a mass threshold of about 30 billion times the mass of the sun, they almost completely stop making new stars. To find out why, Richard Bower at Durham University, UK, simulated the balance of gas entering and leaving the galaxy.
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His team found that once a galaxy gets massive enough, its central black hole ramps up the rate at which it devours the gas around it. This releases a blast of heat, pushing away the cool gas needed to build stars and preventing new material from flowing in (MNRAS, ).
鈥淎ll the gas inside the galaxy flows out into the universe, and there鈥檚 nothing left to form stars anymore,鈥� says Bower.
This article appeared in print under the headline 鈥淪elfish black holes kill host galaxies鈥�