Building a quasar, the brighter type of object in the universe, usually means an end of star formation in a galaxy. Now, new research suggests that some galaxies may continue to generate new stars longer than expected after a quasar disrupts their gas supply.
Using observations from the European Space Agency XMM-Newton Telescope, astronomers in ongoing research have revealed the additional glimmer in the life history of these galaxies. They suspect that unexpected star formation may be possible in all types of galaxies.
"We already knew that quasars were going through a phase of obscured dust … a phase strongly encased in dust supermassive black hole"Kirkpatrick and his colleagues studied several intriguing quasars in X-ray and far-infrared spectra to find quasars that had not lost all their dust. this unique transitional regime that we did not know [about] before, "she said.
Kirkpatrick is calling the new class of objects "cold quasars." She presented her results June 12 at the 234 biannual meeting of the American Astronomical Society in St. Louis.
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A Brief Transition
Quasars or "almost stellar radio sources"form when the material that falls into the supermassive black hole in the center of a galaxy creates an accretion disk.The disc releases an enormous amount of electromagnetic energy, often making the black hole shine even more than its galaxy.
As the infallible gas reaches speed close to the speed of light, the magnetic field around the gas can also be twisted. Material jets can shoot through twisted field lines, choking off the galaxy's gas supply and preventing more gas from falling on it. Without gas, the galaxy can no longer form new starsand becomes a passive dead galaxy.
That is why astronomers worked from the premise that quasars marked galaxies that have aged outside star formation.
But Kirkpatrick and his colleagues began to question this as their data gathered. The process began when they identified several intriguing quasars in the Sloan Digital Sky Survey, the most detailed digital map of the universe.
They also decided to extract data from other instruments, first XMM-Newton Telescope which can detect X-rays that are a key signature of growing black holes. So astronomers used data from the Herschel Space Telescope, a distant infrared instrument, to detect dust and gas in the host galaxy.
Combining all these data sources, scientists' research revealed that about 10 percent of galaxies with supermassive black holes accumulate a source of cold gas and produce new stars.
"That alone is surprising," Kirkpatrick said.
All told, the objects the team studied ran the range of galactic types. Some looked like the Milky Way, with obvious spiral armswhile others were very compact. Others still showed signs of merging with another galaxy. And they all maintained an unexpected supply of cold gas.
"These galaxies are rare because they are in the transition phase – we caught them just before the formation of stars in the galaxy was extinguished," Kirkpatrick said. It estimates that the phase lasted only about 10 million years, a blink of an eye in the Life of 13.8 billion years Of the universe. "It's hard to get these things," she said.
The team's next step will be to try to determine if only certain types of galaxies retain cold gas in the final stage of their life, or if it is something that happens with all galaxies.