Scientists have long believed that the formation of a quasar in a galaxy will sound the death knell of star formation. A new analysis by Allison Kirkpatrick, assistant professor of physics and astronomy at the University of Kansas, suggests that this may not be the case. Kirkpatrick discovered that some galaxies harboring quasars does not seem to have the requirements for a new star formation. This discovery could change the way astrophysicists model the later stages of galactic evolution.
Most large galaxies have supermassive black holes in their centers, but a quasar is a totally different animal. These "quasi-stellar radioelectric sources" have a spiral material accretion disk towards them. Intense X-rays make these galaxies extremely bright and warm, and they capture all the comparatively cold gas of a galaxy that could otherwise form new stars. Often the magnetic field of a quasar is so powerful that it creates a jet of relativistic matter that drains the galaxy of cold gas.
According to Kirkpatrick, most quasars report that a galaxy is over producing new stars, but that does not look like the "off-the-shelf" switch we thought. His analysis of distant galaxies has revealed a population of objects called "cold quasars". The first results of cold quasars appeared in the Sloan Digital Sky Survey, an extremely detailed digital map of the universe. The team described this area of unusual activity in the "Stripe 82" quasars. She used the Newton XMM telescope to study the region and map the locations of growing quasars via X-rays. Then they returned with the Herschel Space Telescope to scan the far-infrared region.
Seeing galaxies in both "hot" X-rays and in the "cold" infrared indicates that there is a star-forming gas supply in active quasar galaxies. According to Kirkpatrick, this does not mean that quasars can exist indefinitely alongside star-forming regions. Over time, they always eliminate cold gases, ending the formation of stars in the galaxy.
Here we are witnessing a new period of transition between the growth of quasars and the end of star formation, which can last up to 10 million years. Only about 10% of the galaxies participating in the study exhibited this behavior. The next step for Kirkpatrick is to determine if specific classes or sizes of galaxies are going through this transition period.