Starbirth in spite of feasting black hole prompts galaxy evolution rethink
Astronomers have found a distant galaxy that has managed to continue making new stars despite the presence of a disruptive "cold quasar" raging at its core. The discovery was made using the airborne SOFIA telescope, which, mounted in the side of a specially modified Boeing 747SP aircraft flying high above the cloud tops, was able to observe infrared light emitted by the distant galaxy.
The universe we observe today is awash with galaxies that are no longer capable of creating new stars. Astronomers believe that the reason for this stagnation lies with the supermassive black holes that sit at the hearts of these monstrous cosmic structures.
In order for new stars to form there must be an abundance of unbound dust and cold gas that can be found in the vast clouds known to populate interstellar space. Over time, gravitational attraction and other catalysts cause the materials that form these stellar nurseries to group together, and eventually coalesce into fully formed stars and solar systems.
However, the voracious feeding habits of supermassive black holes can upset this process, and even shut it down entirely.
As material falls inward towards the black hole and settles into an accretion disk, it begins to spin faster and glow incredibly brightly, releasing massive amounts of energy in the form of electromagnetic radiation. When this feeding happens at a truly enormous scale, the supermassive black hole in question transforms into a quasar, which are the brightest cosmic objects known to exist in the universe.
During this phase of its existence, a quasar would emit a phenomenal amount of energy back out into the surrounding galaxy, in the process warming up or expelling much of the cold star-forming material remaining therein. Ordinarily, this would cripple a galaxy’s ability to produce a new generation of stellar bodies.
However, a new study has revealed that a galaxy located some 5.25 billion light years from Earth designated CQ 4479 has been able to weather the storm as its central supermassive black hole transformed into a quasar, and continue producing new stars.
The authors of the new study drew on infrared data collected by the Stratospheric Observatory for Infrared Astronomy (SOFIA) telescope. Mounted in a specially modified Boeing 747SP aircraft flying high above cloud level, the 2.7-m (8.8-ft) telescope was able to observe the distant galaxy while avoiding 99 percent of Earth’s infrared-blocking atmosphere.
The telescope read the infrared light fingerprint emanating from CQ 4479 in order to determine the amount of interstellar dust and gas present in the galaxy that was still being heated up as a result of the star formation process.
According to the the SOFIA data, the monster lurking at the heart of CQ 4479 is a rare type of quasar known as a cold quasar. This is the term given when a black hole transforms into a quasar, but fails to entirely quench the rate of star birth of its host galaxy.
SOFIA appears to have observed CQ 4479 during a brief window of time in which stars are still able to form as the disruptive effect of the quasar’s feasting rages on before the galaxy succumbs to the destructive effects of the quasar. The authors of the study estimate that the galaxy was creating roughly 100 new Sun-sized stars per year as of the point that the light collected by the flying telescope left its source.
“This shows us that the growth of active black holes doesn’t stop star birth instantaneously, which goes against all the current scientific predictions,” explains 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.”
Follow up studies carried out by the next generation of space-faring observatories, such as the James Webb Space Telescope, will further enhance humanity's understanding of how the monstrous forces unleashed by quasars affect their host galaxies.
The paper has been published in the Astrophysical Journal.