Dramatic collisions of galaxies can provide fireworks shows in more ways than one. New observations have now confirmed a long-theorized link between galaxy mergers and the launch of powerful relativistic jets.
Feeding the Fire
We know that nearly every galaxy hosts a supermassive black hole of millions to tens of billions of solar masses. Some, like the one at the center of our own Milky Way, are quiet. But many actively accrete gas, flaring with bright emission across the electromagnetic spectrum. In addition to accreting material, some of these active galactic nuclei (AGN) also fling incoming material back out, forming powerful jets that zip along at velocities close to the speed of light.
When two galaxies collide, gas can be driven to their centers, feeding the supermassive black holes that lurk there. [NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration]But how does the gas feeding this dramatic AGN activity arrive at the center of the galaxy in the first place? One theory is that violent collisions of galaxies deliver the necessary fuel. In this picture, when two galaxies merge, the turbulent collision feeds gas into the nuclei of the galaxies, causing the AGN to light up and triggering the ...