Scientists have made an exciting discovery: massive collisions between galaxies can spark powerful eruptions in their centers. This breakthrough comes from the Euclid space telescope, a European Space Agency mission aiming to explore dark matter and dark energy by mapping billions of galaxies.
Researchers focused on a portion of one million galaxies observed by Euclid to study active galactic nuclei (AGN). An AGN forms when a supermassive black hole at a galaxy’s center begins to consume large amounts of material. This material spirals into an accretion disk around the black hole. As more gas accumulates, it heats up and glows intensely. Some of these disks even emit beams of particles traveling close to the speed of light, which we call quasars or blazars, depending on their orientation toward Earth.
For a long time, scientists suspected that galaxy mergers could fuel AGN activity, but proving this was challenging. Many powerful AGN are very distant. For instance, the closest known quasar is 2.3 billion light-years away, making it hard to confirm if galaxies are merging from that distance.
The launch of Euclid in 2023 has changed this. With its advanced imaging technology, it can capture vast areas of the sky and provide high-quality images quickly. In just a week, it can cover more ground than the Hubble Space Telescope has in its 35 years of operation.
Using data from Euclid, astronomers categorized the galaxies into two groups: those that appear to be merging and those that don’t. They employed an artificial intelligence tool developed by Berta Margalef-Bentabol and Lingyu Wang from SRON, the Netherlands Institute for Space Research, to identify AGN and measure their energy output. This AI can even detect faint AGN that other methods might miss.
The team discovered a significant difference: galaxies that were merging had between two to six times more AGN compared to those that weren’t. For instance, newly merged galaxies with lots of interstellar dust had six times more AGN. Even in mergers that were nearing completion, there were still twice as many AGN compared to non-merging galaxies.
Antonio la Marca from the University of Groningen noted that some AGN previously thought to be in stable, single galaxies may actually be in galaxies that have already merged. This suggests that mergers could be the main trigger for AGN activity.
An important statistic to consider is that AGN play a crucial role in the evolution of their host galaxies. They can heat up surrounding gas, preventing new star formation. Understanding the connection between AGN and galaxy mergers helps scientists model galaxy evolution better.
These findings are to be published in Astronomy & Astrophysics. For more detailed insights, you can check out their analysis here and information about the AI tool here.
