Black holes aren't just cool and mysterious, but they can also blow winds up to a third of the speed of light. These winds, known as ultra-fast outflows (UFOs), are emitted by supermassive black holes at the center of active galactic nuclei, or quasars. And while they may sound like something out of a sci-fi movie, they actually play an important role in regulating the behavior of these black holes during their active phase.
But what exactly are UFOs, and why are astronomers so interested in studying them? For starters, these gas emissions are thought to fuel the process of star formation in galaxies. However, there's still a lot that we don't know about them, and that's where the SUBWAYS project comes in. The SUBWAYS project is an international research effort dedicated to studying quasars using the ESA's XMM-Newton space telescope. Recently, a group of scholars led by the University of Bologna and the National Institute for Astrophysics (INAF) in Italy shared the first results of this project, which shed new light on the properties of UFOs in 22 luminous galaxies. Using the X-ray Multi-Mirror Mission (XMM), the team analyzed active galactic nuclei (AGN) for a period of more than 1.6 million seconds. Their results showed that in about 30 percent of the AGNs analyzed, there are space winds traveling at speeds of 10 percent to 30 percent of the speed of light. That's fast!
"These results allow us to establish with greater certainty that a significant proportion of active galactic nuclei hosts ultra-fast winds called UFOs, ultra-fast outflows. And we were able to confirm that the intensity of these gas flows is sufficient to significantly change the ecosystem of their galaxies," said Marcella Brusa, a professor at the University of Bologna and INAF associate, who is also the coordinator of the SUBWAYS project. So what does all this mean for the evolution of galaxies? Well, there's a reciprocal relationship between an SMBH and the galaxy surrounding it, where the two influence each other's formation and evolution. While the mechanisms driving this relationship are not yet well understood, the ultra-fast winds emitted by AGNs are thought to play a vital role.
"These observations have allowed us to obtain new independent evidence of the existence of highly ionized matter that is ejected from the innermost regions of active galactic nuclei at speeds close to that of light. These outcomes have allowed us to learn more about these ultrafast winds and to better understand their role in shaping the evolution process of galaxies," said Gabriele Matzeu, a researcher at the University of Bologna, INAF associate, and first author of the paper. In other words, studying UFOs can help us better understand what governs galactic evolution. And who knows, maybe one day we'll even be able to harness the power of these ultra-fast outflows for ourselves. But until then, we'll just have to keep studying and learning.