We often think that galactic developments take a lot of time to happen. It can take thousands or even millions of years for the evolution of stars and galaxies. However, space scientists have recently spotted a unique event wherein six different galaxies that are usually quiet had fired up into active quasars in a matter of months.
The six galaxies had started off as low-ionization nuclear emission line region (LINER) galaxies, which account for one-third of the known galaxies. These LINER galaxies are characterised by the mild activity at their nucleus much lower than quasars.
According to the existing theory, quasars should take thousands of years to fire up. However, astronomers have seen it happen live six times within the first nine months of observations by the Zwicky Transient Facility (ZTF), according to researchers at the University of Maryland.
“For one of the six objects, we first thought we had observed a tidal disruption event, which happens when a star passes too close to a supermassive black hole and gets shredded,” Sara Frederick, graduate student at University of Maryland Department of Astronomy and lead author of the research paper said in a statement.
“But we later found it was a previously dormant black hole undergoing a transition that astronomers call a ‘changing look,’ resulting in a bright quasar. Observing six of these transitions, all in relatively quiet LINER galaxies, suggests that we’ve identified a totally new class of active galactic nucleus,” she added.
To understand how previously quiet galaxy with a calm nucleus can suddenly transition to a bright beacon of galactic radiation, the researchers performed follow-up observations on the objects with the Discovery Channel Telescope. The observations helped in providing clarity to the aspects of the transitions, including how the rapidly transforming galactic nuclei interacted with their host galaxies.
The research team also found that the LINER galaxies are able to host larger black holes at their centres than what was previously thought of. The current theories can not explain how the transition had occurred so fast. Additional studies should reveal further details about life cycles of quasars and the general galaxies.
“These six transitions were so sudden and dramatic, it tells us that there is something altogether different going on in these galaxies. We want to know how such massive amounts of gas and dust can suddenly start falling into a black hole. Because we caught these transitions in the act, it opens up a lot of opportunities to compare what the nuclei looked like before and after the transformation.” Frederick said in the statement.
Their research paper titled “A New Class of Changing-look LINERs” was recently published in The Astrophysical Journal.