by Using the James Webb Space Telescope (JWST), astronomers observed the dramatic “dance” between a supermassive black hole and two satellite galaxies. The observations could help scientists better understand how galaxies and supermassive black holes grew in the early universe.
This supermassive black hole is feeding surrounding matter and powering a bright quasar so far away that JWST can see it as it was less than a billion years after the Big Bang. The quasar, named PJ308-21, is localized to an active galactic nucleus (AGN) in a galaxy that is in the process of merging with two massive satellite galaxies.
Not only did the team determine that the black hole has a mass equal to two billion suns, but they also discovered that the quasar and the galaxies associated with this merger are very developed, surprising considering that they existed when the age was 13.8 years. the cosmos was just an infant.
The merger of these three galaxies is likely to deliver massive amounts of gas and dust to the supermassive black hole, facilitating its growth and allowing it to continue to power PJ308-21.
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“Our study shows that both black holes are in the middle of high redshift [early and distant] The quasars and their host galaxies have already been growing extremely efficiently and rapidly in the first billion years of cosmic history, aided by the rich galactic environment in which these sources are formed,” team leader Roberto Decarli, a researcher at the National Institute of Astrophysics in Italy (INAF), said in a statement.
The data were collected in September 2022 by JWST’s Near InfraRed Spectrograph (NIRSpec) instrument as part of Program 1554, which aims to observe the merger between the host galaxy PJ308-21 and two of its satellite galaxies.
Decarli added that the work represented an “emotional rollercoaster” for the team, who developed innovative solutions to overcome the initial difficulties of data reduction and produce images with an uncertainty of less than 1% per pixel.
Very metal quasar
Quasars are born when supermassive black holes millions or billions of times larger than the sun sit at the heart of galaxies surrounded by a wealth of gas and dust. This material forms a flattened cloud called an accretion disk that surrounds the black hole and gradually feeds it.
The massive gravitational forces of the black hole generate powerful tidal forces in this accretion disk, which heats this gas and dust as much as 120,000 degrees Fahrenheit (67,000 degrees Celsius). This is because the accretion disk emits light across the electromagnetic spectrum. This emission can often be brighter than the combined luminosity of all stars in the surrounding galaxy, making quasars like PJ308-21 some of the brightest objects in the cosmos.
Although black holes do not have characteristics that can be used to determine how advanced they are, their disks (and thus quasars) do. In fact, galaxies can be “aged” in the same way.
The early universe was filled with hydrogen, the lightest and simplest element, and a little helium. This was the basis of the first stars and galaxies, but during the lifetime of these stellar bodies, they created elements heavier than hydrogen and helium, which astronomers call “metals”.
When these stars ended their lives in massive supernova explosions, these metals spread throughout their galaxies and became the building blocks for the next generation of stars. This process saw stars, and through them galaxies, gradually becoming “rich metals.”
The team found that, like most AGNs, PJ308-21’s active core is rich in metals, and the gas and dust around it is being “photoionized.” This is the process by which particles of light, called photons, provide the energy that electrons need to escape from atoms, creating electrically charged ions.
One of the galaxies merging with the host galaxy PJ308-21 is metal-rich, and its material is also being partially photoionized by electromagnetic radiation from the quasar.
Photoionization is also taking place in the second satellite galaxy, but in that case, it is being created by a bout of rapid star formation. This second galaxy also differs from the first and the AGN, as it appears to be metal poor.
“Thanks to NIRSpec, for the first time, we can study, in the PJ308-21 system, the optical band rich in precious diagnostic data on the properties of the gas near the black hole in the galaxy hosting the quasar and in the surrounding galaxies. ,” said INAF staff member and astrophysicist Federica Loiacono. “We can see, for example, the emission of hydrogen atoms and compare it with the chemical elements produced by the stars to find out how rich the gas is in metals.”
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Although this early-universe quasar emits light across a wide range of the electromagnetic spectrum, including optical light and X-rays, the only way to observe it is in infrared.
That’s because, as the light has traveled for over 12 billion years to reach JWST, the expansion of the universe has “stretched” its wavelength significantly. Which “shifts” the light towards the “red end” of the electromagnetic spectrum, a phenomenon known intuitively as “redshift”, which astronomers define as “z”.
JWST is adept at seeing “high-redshift” or “high-z” objects and events like PJ308-21 because of its sensitivity to infrared light.
“Thanks to the sensitivity of the JWST in the near and mid-infrared, it was possible to study the spectra of quasars and companion galaxies with unprecedented precision in the distant universe,” said Loiacono. “Only the excellent ‘view’ offered by JWST can ensure these views.”
The team’s research has been accepted for publication in June 2024 in the journal Astronomy & Astrophysics.
