Most distant high-energy active galaxy discovered

The LST-1 telescope of the Cherenkov Telescope Array “made” the first scientific discovery. Astronomers used telescopes to discover strong radiation from quasar OP 313, making it the most distant active high-energy galaxy known. Active galaxies are galaxies whose core releases large amounts of energy due to processes occurring around a supermassive black hole. Quasar is one of her active galactic nuclei.

The material in the accretion disk attenuates high-energy radiation, so it is hardly detected in high-energy regions. Photons with the highest energy are best absorbed. Furthermore, the further away an object is, the greater the influence of extragalactic background light (EBL) on the high-energy radiation traveling toward us. Extragalactic background light is the sum of radiation from objects outside the Milky Way.

LST-1 observes in the 20-150 gigaelectronvolt range, where high-energy fluxes are less affected by background light. At the beginning of the month, December 1, 2023, astronomers working with the LAT telescope as part of the Fermi gamma-ray telescope reported a change in the activity of source OP 313, i.e. an increase in gamma rays.

The LST-1 telescope observed this object for four days, from December 10th to 14th. Scientists have “captured” radiation exceeding 100 gigaelectronvolts. This means that the energy of these photons is a billion times higher than the energy of the light we see. This places OP 313 at number 10 on the list of known high-energy quasars. Additionally, with a redshift of 0.997, this object is the most distant object of its kind and the second longest source of high-energy radiation. A redshift of 0.997 means that the light from this quasar took about 8 billion years to reach us.

What is important is not the discovery itself, but the fact that the currently operational LST-1 telescope has proven its effectiveness. This is a prototype of his Large Telescope (LST), one of his three types of telescopes in the Cherenkov Telescope Array, an international project to develop a new generation of instruments to study long-range gamma rays. Some of them are located in the northern hemisphere, others in the southern hemisphere.

The LST-1 prototype is the “representative” of the Northern Telescopes, which astronomers primarily use to search for low-energy objects outside our galaxy. Once commissioning is complete, it will be the first of the Cherenkov telescope arrays. In addition to high sensitivity, an important feature of these telescopes is their maneuverability. It can be repositioned within 20 seconds, making it possible to study transient phenomena such as gamma-ray bursts. This means that a series of new discoveries await us.