An article published in “The Astrophysical Journal” reports the discovery of six galaxies with active galactic nuclei (AGN) which showed a remarkable change in their brightness within a few months becoming quasars. A team of researchers used data collected during the first nine months of the Zwicky Transient Facility (ZTF) survey to discover those galaxies that were classified as LINERs, fairly common galaxies that are generally bright but far from quasars. It could be a new kind of activity of the supermassive black holes at the center of those LINER galaxies.
The acronym LINER (Low-ionization nuclear emission-line region) indicates in particular a certain type of galactic nucleus that was identified in about one third of the nearby galaxies. It’s a class that includes quite diverse objects with regard to brightness and shape and there are various discussions about the origin of that brightness and that ionization detected in their nuclei.
The Zwicky Transient Facility (ZTF) survey, which saw the so-called first light on November 1, 2017, aims to detect objects that quickly change brightness using a new camera mounted on the Samuel Oschin Telescope at the Palomar Observatory in California. In early 2018 the first discoveries were announced, a NEO-class (Near-Earth Object) asteroid and a comet, but the discovery of six galaxies that increased their brightness in a few months to the point of becoming quasars is much more Interesting.
The image (Left; infrared & visible light imagery): ESA/Hubble, NASA and S. Smartt (Queen’s University Belfast); (Right; artist’s concept): NASA/JPL-Caltech) shows a LINER-class galaxy during its normal activity on the left and in its artistic representation after becoming a quasar on the right.
Such sudden changes have been detected in Seyfert galaxies, which have active galactic nuclei. The surprise was to detect them in LINER galaxies, which generally have a brightness and activity far lower than quasars’. Sara Frederick of the University of Maryland, lead author of the article, explained that it’s surprising that a galaxy changes its appearance in human time scales in much faster changes than can be explained by current quasar models.
The researchers used the Discovery Channel Telescope for follow-up observations of the six discovered galaxies. They provided confirmation that they have active supermassive black holes at their center, the ones that power the quasar activity by considerably heating materials that orbit them. However, only the closest materials emit light while normally quasars heat those materials up to considerable distances. It’s possible that this black hole activity is expanding and in that case it will be possible to map the development of those new quasars.
The study of the changing look process in those six galaxies will continue for years to see if’t is a new type of active galactic nuclei. The speed of this process is extraordinary for these cosmic phenomena and helps the study of these really extreme objects.