Stunting of black holes explained

A WARMING of the early universe caused by the greediest of black holes could have stunted the growth of the rest. Astronomical surveys suggest that supermassive black holes weighing a billion times more than the sun had formed before the universe was a billion years old. The seeds for these behemoths are thought to be black holes weighing just a few tens of solar masses. To get so big in less than a billion years, the seed black holes must have sucked in gas at a colossal rate. In this scenario, you would expect to see a distribution of black hole masses, with intermediate-sized black holes (those between 105 and 107 solar masses) in numbers orders of magnitude greater than what we see in our local universe. Something must have limited the growth of these black holes. Now Takamitsu Tanaka at the Max Planck Institute for Astrophysics in Garching, Germany, and colleagues have a climate-based explanation. They show that a prodigious amount of X-rays emitted as the supermassive black holes gulped gas would have heated up the universe. Black holes need cool gas to grow so this would have slowed down the growth of other black holes in smaller protogalaxies, even as the growth of black holes in the most massive protogalaxies continued apace . "This global warming process could have basically quenched the latecomers," says Tanaka. "The early ones end up being the monsters and they prevent the overgrowth of the rest."