Home » SUBWAYS project: Shedding light on ultra-fast outflows from supermassive black holes

SUBWAYS project: Shedding light on ultra-fast outflows from supermassive black holes

by News Staff

Ultra-fast outflows (UFOs) are the name given to the gas emissions that originate from the vicinity of supermassive black holes and travel at almost the speed of light. Despite their name, UFOs have nothing to do with aliens, but they play a crucial role in understanding the behavior of active supermassive black holes.

The SUBWAYS (SUper massive Black hole Winds in the x-rAYS) project, an international research effort, has been investigating this phenomenon to shed light on the mechanisms that regulate active supermassive black holes. The first results of this project have been published in two papers in Astronomy & Astrophysics. The first paper, led by scholars from the University of Bologna and INAF, analyzed data from ESA’s XMM-Newton space telescope.

The study focused on 22 active galactic nuclei (AGN), which are regions surrounding supermassive black holes emitting enormous amounts of radiation across the electromagnetic spectrum during the active phase. The investigation revealed that approximately 30% of the AGN analyzed had UFOs traveling at speeds between 10% and 30% of the speed of light.

According to Marcella Brusa, a professor at the University of Bologna and coordinator of the SUBWAYS project, the recent findings provide greater certainty about the existence of ultra-fast winds known as UFOs in a significant number of active galactic nuclei. These ultra-fast outflows have the potential to significantly impact the ecosystem of their respective galaxies.

Artistic view of multiphase AGN-driven winds highlighting the different phases and scales that are involved in the outflow. The wind propagates from the central engine (< 1 pc; a), through the surrounding ISM (1 pc–1 kpc; b), out to the boundaries of the host galaxy (> 10 kpc; c). SUBWAYS will investigate the outflow in its launching phase, when the gas is highly ionized, and the presence of fast moving material can be revealed in X-rays. (figure adapted from Cicone et al. 2018, Nat. As. 2, 176). Credit: University of Bologna

The relationship between a supermassive black hole and its surrounding galaxy is mutually influential and poorly understood. However, the emission of ultra-fast winds from active galactic nuclei could be a critical component in understanding the mechanisms driving this relationship. The SUBWAYS project’s findings shed light on the importance of UFOs in the formation and evolution of supermassive black holes and their surrounding galaxies.

UFOs, or ultra-fast outflows, are produced when gas is expelled from the accretion disk surrounding supermassive black holes, transferring energy and matter into space. This mechanism is crucial in regulating star formation processes.

Scientists analyze X-ray spectra to detect UFOs, searching for absorptions created by highly ionized materials like iron. These absorptions are caused by the extreme temperatures, reaching tens of millions of degrees, generated near supermassive black holes.

The SUBWAYS project utilized the ESA XMM-Newton X-ray Space Telescope to conduct an extensive 18-day observation of 17 active galactic nuclei located between 1.5 to 5 billion light years away. By analyzing X-ray spectra for absorptions caused by highly ionized materials like iron, the team was able to detect the presence of ultra-fast outflows (UFOs) from these galaxies’ innermost regions. This discovery sheds new light on the role of these powerful emissions in regulating star formation and shaping the evolution of galaxies. The research findings were published in Astronomy & Astrophysics in two papers, with the first article focusing on the statistics of UFOs in quasars beyond the local universe, while the second article studied lower-velocity and lower-ionization gas flows visible in the ultraviolet band using the HST satellite.

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