Galaxies may be more heavily influenced by the black holes inside them than previously thought. New research indicates that supermassive black holes can blast gas and dust out of their host galaxies. In fact, the black hole blowhards can eject so much of a galaxy's star-building materials that they halt star formation all together.
Virtually all galaxies have black holes at their center. Scientists call a galaxy "active" when that black hole is actively consuming large amounts of gas, creating an area of intense brightness around it called the active galactic nucleus. But even though the black holes in an active galaxy are "massive," and indeed quite active, they're still relatively tiny compared to the galaxy as a whole. So scientists aren't quite clear on just how much influence these black hole cores have on the way a galaxy forms, lives, and dies.
In a study published Wednesday in Nature, researchers have for the first time observed a link between the powerful winds of an active black hole and the ejection of star-making materials from its host galaxy. In other words, these black holes can basically nix star formation for good, limiting the host galaxy's size.
To lead author Francesco Tombesi of NASA’s Goddard Space Flight Center and the University of Maryland, the find hints at an intriguing symbiotic relationship between black holes and galaxies.
"This indicates that when we think about galaxies and super massive black holes, we are in some ways thinking of the same thing," he said, "One goes with the other -- almost like an atom with electrons around it. You can't consider one without the other."
This isn't exactly shocking news, and other researchers have theorized that black holes might hold this influence over galaxies for some time. But Tombesi's team is the first to actually observe the wind caused by the black hole at the same time as the galaxy's outpouring of gas. It spotted the phenomenon by turning Suzaku, a satellite operated by the Japan Aerospace Exploration Agency and NASA, towards a chaotic galaxy called IRAS F11119+3257.
"These are not like normal spiral or elliptical galaxies. They're like train wrecks," study author Sylvain Veilleux, a professor of astronomy at U-Md. and a fellow at the Joint Space-Science Institute, said in a statement. "Two galaxies collided with each other, and it's now a single object. This train wreck provided all the material to feed the supermassive black hole that is now driving the huge galactic-scale outflow."
So there was plenty of fuel for the black hole to take in, leading to violent winds that pushed galactic building materials out until star formation slowed and stopped.
The team members hope to find more examples of this black hole push and pull now that they know what to look for. But Tombesi thinks the findings should encourage all researchers studying galaxies to keep an eye on black holes.
"It's very important for making simulations of a galaxy, and when studying observations, to keep this in mind," he said. "And if people see some phenomenon and don't know the origin. . . we now know that the black hole itself is powerful enough to cause big changes in a galaxy. Maybe it's worth looking to the black hole as the source of other phenomenon."