Paired rays of matter moving away from supermassive black holes in the center of galaxies usually extend in opposite directions along the axis of rotation of the black hole, as in the two images in the lower galaxy. But some, like the two upper galaxies, have jets bent at odd angles. Image by Melissa Morris, UW – Madison
The most active, gluttonous black holes in the universe can often be found with two jets of matter flowing from their centers. These jets accelerate with astonishing speed into space in opposite directions, and are usually aligned along the axis of the rotating black hole. But not always.
Some of these supermassive black galaxy hearts, called active galactic nuclei, have jets bent at mysteriously strange angles. New research from astronomers at the University of Wisconsin-Madison, recently published in The Astronomical Journal, shows that these jets are likely to be doubled by a combination of their galaxies moving at enormous speed and to drag the jets as they move to through intergalactic gas clouds. .
Melissa Morris
“These active galactic nuclei are a subset of black holes that, even for black holes, are very quickly devouring a huge amount of matter,” says Melissa Morris, a graduate student in astronomy at UW-Madison and lead author of the new study. “They’re feeding so fast that a ton of energy is released into the area around the black hole. That’s what causes these wild AGN planes.”
Understanding the environment that forms the direction of lightning helps astronomers understand how galaxies evolve, but the question of how matter is thrown out of a black hole is an open question. Supermassive black holes are at the center of almost every large galaxy.
But no matter how the jets form, astronomers find them useful. The incredibly hot plasma in the jets produces radio waves that astronomers can observe reaching far outside their galaxies, pointing back toward the centers of the galaxies that produce them as useful arrows on an empty map.
“It’s not always easy to see things in space. Sometimes you have to be creative, “says Morris.” The fact that we can “see” these jets (we can pick up the radio waves they produce) means we can also see them interacting with things that exist outside the galaxy. “
This makes the cause of bent jets especially interesting, and why UW-Madison researchers, including astronomy professors Eric Wilcots and Sebastian Heinz and staff scientist Eric Hooper, set out to find out if anything about the environment of the galaxies is pushing the jets.
“The fact that we can see them bending probably means we can infer something about their surroundings,” Morris says. “But can we be sure?”
Using expansive 3D maps of the universe, the Sloan Digital Sky Survey, and the FIRST Radio Survey, Morris compiled a list of 160 galaxies with powerful radio-emitting jets that are also folded. From other star catalogs, he built a group of galaxies with unfolded jets to compare.
For each galaxy, astronomers used a technique called the peer-to-peer algorithm to identify each neighboring galaxy within a given search radius, and then each neighbor of each of those galaxies within the radius, repeating the hunt. until there were no more neighbors. to the chain.
A cluster of very close-knit galaxies is more likely to be thick with gas and dust, the kind of dense environment astronomers expected could push a lightning AGN slightly off-axis. Indeed, AGNs with unfolded jets were more likely to be alone or paired with another galaxy. Jumping AGNs were more likely to be combined with clusters of three or more galaxies.
An AGN zooming through space at high speed is also likely to have jets that appear to bend, as the ends come out and appear to follow behind the moving galaxy core. Thus, astronomers also compared the relative brightness of the galaxies they studied. The brightest galaxies are usually more massive. The largest galaxy in a cluster is the group’s anchor, which is at the center of the cluster members’ interactions. The faintest and lightest galaxies would be launched faster through their neighborhood.
“The brightest galaxy in a cluster is a kind of head, with the other galaxies moving around it,” says Morris. “And we saw that more than 90 percent of our un-bent AGNs in groups were the brightest in the cluster. They probably don’t move fast enough to make their jets look bent.”
It is likely to be a combination of gas-heavy, high-velocity surrounding space that twists the jets of an AGN.
“It’s an act of balancing,” Morris says. “If you have a super dense medium to pass through, it wouldn’t take a ton of speed to make bent jets. And galaxies moving at high speed wouldn’t need as much gas as having an AGN with a bend.
Researchers continue to discover the relative influence of different conditions.
“We can’t see how a single galaxy changes over time. It takes billions and billions of years,” says Morris. “So the better we can determine what made certain types of galaxies look different than others, the better we can understand how they evolve and interact.”