The hungriest of black holes are thought to gobble up so much surrounding material they put an end to the life of their host galaxy. This feasting process is so intense that it creates a highly energetic object called a quasar – one of the brightest objects in the universe – as the spinning matter is sucked into the black hole’s belly. Now, researchers have found a galaxy that is surviving the black hole’s ravenous forces by continuing to birth new stars – about 100 Sun-sized stars a year.
The discovery from NASA’s telescope on an airplane, the Stratospheric Observatory for Infrared Astronomy, can help explain how massive galaxies came to be, even though the universe today is dominated by galaxies that no longer form stars. The results are published in the Astrophysical Journal.
“This shows us that the growth of active black holes doesn’t stop star birth instantaneously, which goes against all the current scientific predictions,” said Allison Kirkpatrick, assistant professor at the University of Kansas in Lawrence Kansas and co-author on the study. “It’s causing us to re-think our theories on how galaxies evolve.”
SOFIA, a joint project of NASA and the German Aerospace Center, DLR, studied an extremely distant galaxy, located more than 5.25 billion light years away called CQ4479. At its core is a special type of quasar that was recently discovered by Kirkpatrick called a “cold quasar.” In this kind of quasar, the active black hole is still feasting on material from its host galaxy, but the quasar’s intense energy has not ravaged all of the cold gas, so stars can keep forming and the galaxy lives on. This is the first time researchers have a detailed look at a cold quasar, directly measuring the black hole’s growth, star birth rate, and how much cold gas remains to fuel the galaxy.
“We were surprised to see another oddball galaxy that defies current theories,” said Kevin Cooke, postdoctoral researcher at the University of Kansas in Lawrence, Kansas, and lead author of this study. “If this tandem growth continues both the black hole and the stars surrounding it would triple in mass before the galaxy reaches the end of its life.”
As one of the brightest and most distant objects in the universe, quasars, or “quasi-stellar radio sources,” are notoriously difficult to observe because they often outshine everything around them. They form when an especially active black hole consumes huge amounts of material from its surrounding galaxy, creating strong gravitational forces. As more and more material spins faster and faster toward the center of the black hole, the material heats up and glows brightly. A quasar produces so much energy that it often outshines everything around it, blinding attempts to observe its host galaxy. Current theories predict that this energy heats up or expels the cold gas needed to create stars, stopping star birth and driving a lethal blow to a galaxy’s growth. But SOFIA reveals there is a relatively short period when the galaxy’s star birth can continue while the black hole’s feast goes on powering the quasar’s powerful forces.
Rather than directly observing the newborn stars, SOFIA used its 9-foot telescope to detect the infrared light radiating from the dust heated by the process of star formation. Using data collected by SOFIA’s High-resolution Airborne Wideband Camera-Plus, or HAWC+ instrument, scientists were able to estimate the amount of star formation over the past 100 million years.
“SOFIA lets us see into this brief window of time where the two processes can co-exist,” said Cooke. “It’s the only telescope capable of studying star birth in this galaxy without being overwhelmed by the intensely luminous quasar.”
The short window of joint black hole and star growth represents an early phase in the death of a galaxy, wherein the galaxy has not yet succumbed to the devastating effects of the quasar. Continued research with SOFIA is needed to learn if many other galaxies go through a similar stage with joint black hole and star growth before ultimately reaching the end of life. Future observations with the James Webb Space Telescope, which is scheduled to launch in 2021, could uncover how quasars affect the overall shape of their host galaxies.
Reference : “Dying of the Light: An X-Ray Fading Cold Quasar at z ~ 0.405” by Kevin C. Cooke, Allison Kirkpatrick, Michael Estrada, Hugo Messias, Alessandro Peca, Nico Cappelluti, Tonima Tasnim Ananna, Jason Brewster, Eilat Glikman, Stephanie LaMassa, T. K. Daisy Leung, Jonathan R. Trump, Tracey Jane Turner and C. Megan Urry, 6 November 2020, Astrophysical Journal.
SOFIA is a joint project of NASA and the German Aerospace Center. NASA’s Ames Research Center in California’s Silicon Valley manages the SOFIA program, science, and mission operations in cooperation with the Universities Space Research Association, headquartered in Columbia, Maryland, and the German SOFIA Institute at the University of Stuttgart. The aircraft is maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California. The HAWC+ instrument was developed and delivered to NASA by a multi-institution team led by NASA’s Jet Propulsion Laboratory (JPL).