Researchers using the James Webb Space Telescope have probed the interaction of a quasar with satellite galaxies, revealing critical insights into the early growth of galaxies in the universe, black hole mass and chemical evolution. (Artist’s concept.) Credit: SciTechDaily.com
An international research group used The James Webb Space Telescope to witness the dramatic interplay between a quasar within the PJ308–21 system and two massive satellite galaxies in the distant universe
This research has revealed important details about the formation of galaxies, the mass and growth of supermassive black holes, and the chemical properties of these celestial bodies, marking a major step forward in understanding cosmic history.
A global team led by the Italian National Institute for Astrophysics (INAF) and made up of 34 research institutes and universities around the world used the Near Infrared Spectrograph (NIRSpec) on board the James Webb Space Telescope (JWST) to witness the interaction dramatic between a quasar within. the PJ308–21 system and two massive satellite galaxies in the distant universe. The observations, carried out in September 2022, revealed unprecedented and awe-inspiring details, providing new insights into the growth of galaxies in the early universe. The results were presented during the 2024 European Astronomical Society (EAS) meeting in Padua (Italy) and published on July 5 in Astronomy and Astrophysics.
Quasar Discovery and Galaxy Dynamics
Observations of this quasar (already described by the same authors in another study published last May), one of the first studied with NIRSpec when the universe was less than a billion years old (redshift z = 6.2342) , have discovered data of sensational quality: the instrument “captured” the spectrum of the quasar with an uncertainty of less than 1% per pixel. The host galaxy of PJ308-21 shows high metallicity and photoionization typical of an active galactic nucleus (AGN), while one of the satellite galaxies exhibits low metallicity (referring to the abundance of chemical elements heavier than hydrogen and helium) and photoionization caused by star formation; a higher metallicity characterizes the second satellite galaxy, which is partially photoionized by the quasar.
Map of the hydrogen (in red and blue) and oxygen (in green) emission lines in the PJ308-21 system, shown after masking the light from the central quasar (“QSO”). The different colors of the quasar’s host galaxy and companion galaxies in this map reveal the physical properties of the gas within them. Credit: Decarli/INAF/A&A 2024
Insights into Cosmic Evolution
The discovery has enabled astronomers to determine the mass of the supermassive black hole in the center of the system (about 2 billion solar masses). It also confirmed that the quasar and the surrounding galaxies are highly developed in mass and metal enrichment and continuously growing. This has profound implications for our understanding of the cosmic history and chemical evolution of galaxies, highlighting the transformative impact of this research.
Technical advances in space observations
Roberto Decarli, a researcher at INAF in Bologna and first author of the paper, explains: “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 rapid accretion. turbulent already in the first billion years of cosmic history, aided by the rich galactic environment in which these sources form.
The data were acquired in September 2022 as part of the 1554 Program, one of nine Italian-led projects of the JWST’s first observing cycle. Decarli runs this program to observe the merger between the quasar’s host galaxy (PJ308-21) and two of its satellite galaxies.
Map of ionized oxygen emission in the PJ308-21 system, observed with the James Webb Space Telescope. Each frame shows a different speed range. In the animation, we see the complex three-dimensional structure of the system and the “cosmic dance” of satellite galaxies around the quasar. Credit: Decarli/INAF/A&A 2024
Advancing Astrophysics with the James Webb Space Telescope
The observations were carried out in integral field spectroscopy mode: for each image pixel, the spectrum of the entire optical band (in the rest frame of the source) can be observed, shifted towards the infrared by the expansion of the universe. This allows the study of different gas tracers (emission lines) using a 3D approach. Thanks to this technique, the INAF-led team discovered spatially extended emissions from various elements, which were used to study the properties of the ionizing interstellar medium, including the source and strength of the photoionizing radiation field, metallicity, dust obscuration, density of electrons and the temperature and rate of star formation. In addition, the researchers marginally detected the emission of starlight associated with companion sources.
Federica Loiacono, astrophysicist, researcher and postdoctoral fellow working at INAF, enthusiastically comments on the results: “Thanks to NIRSpec, for the first time we can study in the PJ308-21 system the optical band, rich in valuable diagnostic data for gas properties near the black hole in the galaxy hosting the quasar and in the surrounding galaxies. We can, for example, look at the emission of hydrogen atoms and compare it to the chemical elements produced by stars to determine how metal-rich the gas in galaxies is. The experience in the reduction and calibration of 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. Federica Loiacono is the Italian contact person for NIRSpec data reduction at the INAF JWST Support Center.
Future Directions and Implications
She adds: “Thanks to the near- and mid-infrared sensitivity of the James Webb Space Telescope, it was possible to study the spectrum of the quasar and its companion galaxies with unprecedented precision in the distant universe. Only the excellent ‘view’ provided by JWST, with its unparalleled capabilities, could provide these observations.” The work represented a “real emotional roller coaster,” continues Decarli, “with the need to develop innovative solutions to overcome initial difficulties in data reduction”.
This transformative impact of the instruments on board the James Webb Space Telescope underscores its crucial role in advancing astrophysical research: “Until a few years ago, data on metal enrichment (essential for understanding the chemical evolution of galaxies) was almost beyond reach. ours. 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 in its infancy,” concludes Decarli.
Reference: “A quasar-galaxy merger at z~6.2: Rapid accretion of the host via the accretion of two massive satellite galaxies” by Roberto Decarli, Federica Loiacono, Emanuele Paolo Farina, Massimo Dotti, Alessandro Lupi, A. Romain Meyer, Marco Mignoli , Antonio Pensabene, A. Michael Strauss, Bram Venemans, Jinyi Yang, Fabian Walter, and Julien Wolf, 2 Jul 2024, Astronomy and Astrophysics.
DOI: 10.1051/0004-6361/202449239