SOFIA opens a surprising window on quasars and galactic evolution

An artist’s impression of quasar CQ4479, a galaxy hosting a ravenous supermassive black hole. As material falls toward the center, it is heated to extreme temperatures producing a flood of radiation thought to kill star birth by driving off or heating up the necessary raw materials. But the SOFIA airborne observatory has allowed astronomers to study an intermediate state, one in which the supermassive black hole and star birth coexist. Image: NASA/ Daniel Rutter

Quasars are galaxies hosting supermassive black holes that radiate so much energy as they consume galactic debris that they heat up or expel gas that otherwise would be available for star formation, bringing the host galaxy’s growth to an end. But astronomers have now found a missing link of sorts, a so-called “cold quasar” in which star formation has managed to continue even in the presence of a ravenous supermassive black hole.

“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 of a study in The Astrophysical Journal. “It’s causing us to re-think our theories on how galaxies evolve.”

Kirkpatrick and her colleagues used the NASA-German Aerospace Center Stratospheric Observatory for Infrared Astronomy, or SOFIA, to study a quasar some 5.25 billion light years away known as CQ4479.

Infrared light emitted by dust that was heated up by the process of star formation, not the central black hole, allowed the researchers to estimate the rate of star birth over the past 100 million years, concluding CQ4479 is building about 100 Sun-size stars each year.

“SOFIA lets us see into this brief window of time where the two processes can co-exist,” said lead author Kevin Cooke, a postdoctoral researcher at the University of Kansas. “It’s the only telescope capable of studying star birth in this galaxy without being overwhelmed by the intensely luminous quasar.”