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Webb describes the collision of a quasar with satellite galaxies in the early universe

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PJ308–21 system, photographed by Webb. Credit: Decarli/INAF/A&A 2024

An international team of astronomers has used A near-infrared spectrograph (NIRSpec) aboard the Webb Space Telescope observed a dramatic collision in the early universe between a single quasar and two massive satellite galaxies. This applies to the PJ308–21 system, which was spotted with Webb as early as September 2022 and the results of which were announced last week at a council meeting. European Astronomical Society (EAS 2024) in Padua (Italy). The measured redshift of the quasar is z = 6.12342, which means that it already existed when the universe was less than a billion years old (about 13 billion years ago). With NIRSpec, it was possible to image the spectrum of the quasar with amazing precision: the uncertainty was only 1% per pixel! The parent galaxy of the PJ308–21 system is an Active Galactic Nucleus (AGN), as it is called, a quasar with a supermassive black hole that is highly active due to its intake of matter.

Many metals, which are elements heavier than helium, have been found in quasars. Few metals were found in one of the satellite galaxies that the quasar collided with. Another satellite system contains metals, but is likely also affected by a nearby quasar. Photoionization also occurs in that satellite and quasar. which occurs due to the intense UV radiation of newly formed stars. The black hole in the quasar turns out to be two billion solar masses, much heavier than Sgr A*, the black hole at the core of the Milky Way galaxy, which is more than four million solar masses. Satellite galaxies also have a lot of mass and are still growing. Roberto Decarli (INAF in Bologna) and his team made the observations. In the video above you can see observations of ionized oxygen in the system.

More information about the collision of the system can be found in the professional article A quasar-galaxy Merger at z~6.2: Rapid host growth via accretion of two massive satellite galaxies by Roberto Decarli et al. Astronomy & Astrophysics (2024).



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