An international research team, led by the Italian National Institute for Astrophysics (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 within the System PJ308-21.
This remarkable discovery provides new insights into the growth of galaxies in the early universe, providing a glimpse into the processes that shaped the cosmos during its formative years.
Observation of quasar-galaxy interaction
In September 2022, JWST’s Near Infrared Spectrograph (NIRSpec) observed PJ308-21 system, revealing 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 incredible precision.
The NIRSpec instrument captured the spectrum of the quasar with an uncertainty of less than 1% per pixel, allowing researchers to study the physical properties of the gas inside the quasar’s host galaxy and its companion galaxies. This high level of detail has provided invaluable data that helps to understand the early stages of galaxy formation and the role of quasars in this process.
High metallicity and star formation
The host galaxy of PJ308-21 exhibits high metallicity and photoionization conditions typical of an active galactic nucleus (AGN), while one of the satellite galaxies shows low metallicity and photoionization caused by star formation. The second satellite galaxy, partially photoionized by the quasar, also exhibits high metallicity.
These observations confirm that both the quasar and surrounding galaxies are highly evolved in terms of mass and metal enrichment and are undergoing continuous growth. Roberto Decarli, a researcher at INAF and lead author of the study, stated: “Our study reveals that both the black holes at the center of high-redshift quasars and the galaxies that host them undergo extremely efficient and turbulent 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 projects led by Italy in the first observation cycle of JWST. The team used integral-field spectroscopy, allowing them to observe the spectrum of the entire optical band for each image pixel.
This technique enabled the study of various gas tracers and their properties ionized interstellar mediumincluding metallicity, dust obscuration, electron density and temperature, and star formation rate.
Federica Loiacono, an astrophysicist and researcher at INAFemphasized the importance of these observations: “Thanks to NIRSpec, for the first time we can study in the PJ308-21 system the optical band, rich in valuable diagnostic data for the properties of the gas near the black hole in the galaxy hosting the quasar. and in surrounding galaxies we can see, for example, the emission of hydrogen atoms and compare that with the chemical elements produced by stars to determine how metal-rich the gas in the galaxy is.”
Insights from Advanced Data Analytics
The data collected through these observations have allowed researchers to dig deep into the conditions and processes that occur in it these early galaxies. By studying the emission lines of various elements, the team was able to determine the properties of the ionized interstellar medium, such as the source and intensity of photoionizing radiation, metallicity levels, and electron density and temperature.
This detailed analysis gives 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 the first collected with NIRSpec in integral field spectroscopy mode, has provided a strategic advantage for the Italian community in managing similar data from other programs,” Loiacono said. .
Implications for cosmic history
The ability to study the chemical composition and physical properties of galaxies in such detail has profound implications for our understanding of cosmic history and the chemical evolution of galaxies. Data collected from 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 only a few hours of observation, even in galaxies observed when the universe was in its infancy.”
This ability to measure and analyze the chemical properties of early galaxies opens new avenues for understanding the processes that guided their formation and evolution.
The transformative impact of the James Webb Space Telescope
Findings from this study not only shed light on early growth and development galaxies and black holes but also demonstrate the transformative impact of the advanced capabilities of the James Webb Space Telescope.
JWSTs sensitivity in the near- and mid-infrared spectra allows unprecedented precision in observing distant objects, making it possible to collect detailed data that was previously unattainable. “The work represented a real ’emotional roller coaster,’ with the need to develop innovative solutions to overcome the initial difficulties in data reduction,” said Decarli, highlighting the challenges and triumphs of the research process.
like JWST continues to survey the universe, is expected to reveal further groundbreaking discoveries that will deepen our understanding of the cosmos and the fundamental processes that shaped its evolution.
