Today is one of those delightful days when we get to actually do one of those things we always say we’re going to do: we get to revisit a story we first introduced back in May of 2021. This is the story of galaxies with bent jets.

First some background: When material falls into a black hole, it can’t fall straight in due to the ever-annoying property of angular momentum. Instead, the material gets caught up in spiraling orbits, where it gets hot and dense. Magnetic fields get involved, and pretty soon, this disk of material is acting like a rail gun that fires electrons out of galaxies along the rotation axis of the systems. These electrons in motion end up radiating away radio signals, and thus, we see galaxies with jets when we look at the sky with radio eyes.

And most of the time these arms are sticking straight out of the galaxies like epic fountains, but sometimes, they are bent into all sorts of weird shapes.

And in new research coming from Mellisa Morris, these twisted systems are just drawing attention to their environment. When a radio galaxy exists in a fairly empty region of space, it won’t be moving very fast, and there won’t be a lot for it to interact with. Thus, low-density environments give us galaxies with those classic straight jets.

Put that same galaxy in the environment of a galaxy cluster, and it will accelerate to high velocities and be buffeted by surrounding material as it falls toward the cluster’s center. These galaxies, like a fountain in a hurricane, will have jets bent in myriad directions by this one-two punch of motion and external forces.

And while it is tempting to say that, thus, high-density environments give us the curly wurly galaxy jets, there is a fascinating exception. That massive galaxy that sits in the gravitational sweet spot in the center of a cluster doesn’t really move. It just grows, and when it eats, it produces some of the mightiest jets in the universe and sends them powering out like water cannons beaming material straight into their surroundings.

So there can be multiple reasons a galaxy develops those boring straight jets, but only one reason – so far – for all the brilliantly twisted other shapes they can make.

More Information

University of Wisconsin-Madison press release

“How Does Environment Affect the Morphology of Radio AGN?“, Melissa Elizabeth Morris, Eric Wilcots, Eric Hooper, and Sebastian Heinz, 2022 May 19, The Astronomical Journal