An international research team, led by the Italian National Astrophysical Institute (INAF), has used the James Webb Space Telescope (JWST) to capture an extraordinary event in the distant Universe: the dramatic interaction between a quasar and two massive satellite galaxies in the PJ308-21 system.
This remarkable discovery provides new insights into the growth of galaxies in the early universe and offers a glimpse into the processes that shaped the cosmos during its formative years.
Observing the interaction between quasar and galaxy
In September 2022, the JWST Near infrared spectrograph (NIRSpec) observed the PJ308-21 systemthat revealed unprecedented details about this quasar-galaxy merger. The quasar, located in a galaxy that existed when the universe was less than a billion years old, was observed with remarkable precision.
The NIRSpec instrument captured the quasar’s spectrum with an uncertainty of less than 1% per pixel, allowing researchers to study the physical properties of the gas in the quasar. the quasar’s host galaxy and their associated galaxies. This high level of detail has provided valuable data to help understand the early stages of galaxy formation and the role of quasars in this process.
High metal content and star formation
The host galaxy of PJ308-21 exhibits high metallicity and photoionization conditions characteristic of an active galactic nucleus (AGN), while one of the satellite galaxies exhibits low metallicity and star formation-induced photoionization. The second satellite galaxy, partially photoionized by the quasar, also exhibits high metallicity.
These observations confirm that both the quasar and the surrounding galaxies are highly evolved in terms of mass and metal enrichment, and undergo constant growth. Roberto Decarli, a researcher at INAF and the lead author of the study, explained: “Our study reveals that both the black holes at the centre of high-redshift quasars and the galaxies that host them undergo extremely efficient and tumultuous growth already in the first billion years of cosmic history, aided by the rich galactic environment in which these sources form.”
Innovative techniques for detailed analysis
The observations were carried out as part of one of nine Italian-led projects in the first observation cycle of the JWSTThe team used integral field spectroscopy, which allowed them to observe the spectrum of the entire optical band for each image pixel.
This technique made it possible to study different gas tracers and the properties of the ionized interstellar mediumincluding metal content, dust obscuration, electron density and temperature, and star formation rate.
Federica Loiacono, astrophysicist and researcher at INAFemphasized the importance of these observations: “Thanks to NIRSpec, we can study for the first time in the PJ308-21 system the optical band, rich in valuable diagnostic data on the properties of the gas near the black hole in the galaxy hosting the quasar and in the surrounding galaxies. For example, we can see the emission of hydrogen atoms and compare it with the chemical elements produced by the stars to determine how rich the gas in galaxies is in metals.”
Insights from advanced data analytics
The data collected through these observations have enabled researchers to conduct in-depth studies of the conditions and processes occurring in these early galaxiesBy studying the emission lines of different elements, the team was able to determine the properties of the ionized interstellar medium, such as the source and intensity of photoionizing radiation, the metal abundances, and the density and temperature of electrons.
This detailed analysis provides a clearer picture of the physical conditions in the galaxies and how they interact with the quasar at their center. “The experience in reducing and calibrating these data, some of which were the first to be collected with NIRSpec in integral field spectroscopy mode, has provided a strategic advantage for the Italian community in managing similar data from other programs,” said Loiacono.
Implications for cosmic history
The ability to study the chemical composition and physical properties of galaxies in such detail has major implications for our understanding of cosmic history and the chemical evolution of galaxies. The data provided by the JWST allows astronomers to map the metal enrichment in galaxies observed when the universe was still in its infancy.
Roberto Decarli noted: “Until a few years ago, data on metal enrichment (essential for understanding the chemical evolution of galaxies) were almost beyond our reach, especially at these distances. Now we can map them in detail with just a few hours of observation, even in galaxies observed when the Universe was still in its infancy.”
This ability to change the chemical properties of early galaxies opens up new possibilities for understanding the processes that determine their origin and evolution.
The Transformative Impact of the James Webb Space Telescope
The findings of this study not only shed light on the early growth and development of galaxies and black holes but also demonstrate the transformative impact of the advanced capabilities of the James Webb Space Telescope.
The JWST’s sensitivity in the near and mid-infrared spectrum provides unprecedented precision in observing distant objects, making it possible to collect detailed data that were previously inaccessible. “The work was a real ’emotional rollercoaster’, with the need to develop innovative solutions to overcome the initial difficulties in reducing data,” Decarli shared, highlighting the challenges and triumphs of the research process.
If the JWST As the universe continues to be studied, it is expected to yield even more groundbreaking discoveries that will deepen our understanding of the cosmos and the fundamental processes that have shaped its evolution.