Quasars are believed to be the most luminous source of light in the cosmos. Almost all galaxies in the universe are said to have one quasar. Astronomers have managed to identify more than a million quasars until now.
These bodies are formed when a supermassive black hole that is at the center of a galaxy has enough material around it that gets sucked into the accretion disc to generate energy to power it. Scientists are yet to determine why changing-look quasars switch between a state of high radiance and low luminosity.
New method proves helpful
With low brightness, a quasar is too faint to be seen against the backdrop of the galaxy it belongs to, making it difficult for space scientists to find the supermassive black hole it is associated with. Scientists from the University of Bath have found a new technique to pinpoint rare extragalactic objects including the changing-look quasars.
This new method will enable astronomers to find quasars undergoing extreme changes in their light intensity. With this, they will be able to create a more comprehensive census of supermassive black holes. To get a better understanding of how supermassive black holes grow, scientists will have to determine the cause behind the change in luminosity.
Four new quasars located
“These quasars and supermassive black holes are extremely important for galaxy evolution—the more we learn about them, the more we understand how they influence the growth of galaxies,” said Astrophysicist Dr. Carolin Villforth.
For the study, the team of scientists used spectroscopic data to examine the alterations in minimal wavelength ranges. It allowed them to detect change-look quasars that previous searches failed to do. This method also allowed scientists to spot 4 changing-look quasars that are located millions of light-years away from our planet. They were too dim to have been spotted in the photometric searches.
“We took a previous dataset and applied our new method to see if we could identify any new changing quasars that others had missed. This gave us a bigger set of changing-look quasars for further study and validated that our methodology was more sensitive than others, which was great. It shows that our methodology is more sensitive to weaker luminosity,” said, Bart Potts, lead author of the study.
