What To Know
- An international research group led by the Italian National Institute of Astrophysics (INAF) used the Near Infrared Spectrograph (NIRSpec) of the James Webb Space Telescope (JWST) to observe a quasar located in the PJ308-21 system that was interacting with two massive satellite galaxies.
- With higher metallicity, the second satellite galaxy is partially photoionized by the quasarThese observations then allowed astronomers to determine the mass of the supermassive black hole at the center of the system which rises to about two billion solar massesThe results confirm that the quasar and surrounding galaxies are highly evolved in terms of mass and metal enrichment, and continue to grow significantly.
- ” Thanks to NIRSpec, we can for the first time study the optical band in the PJ308-21 system, rich in data on the properties of the gas near the black hole in the galaxy hosting the quasar and in the surrounding galaxies.
An international research group led by the Italian National Institute of Astrophysics (INAF) used the Near Infrared Spectrograph (NIRSpec) of the James Webb Space Telescope (JWST) to observe a quasar located in the PJ308-21 system that was interacting with two massive satellite galaxies. These observations, carried out in September 2022, then offered new insights into the growth of galaxies in the early Universe.
Quasar PJ308-21 and its satellite galaxies
A quasar is a galactic core extremely bright powered by a supermassive black hole. The latter accretes surrounding matter and releases an enormous amount of energy in the form of light and radiation, often surpassing the luminosity of the entire galaxy that hosts it. Quasars are thus considered to be the brightest and most energetic objects in the Universe. Studying these objects allows us to better understand the formation and evolution of galaxies as well as the role of supermassive black holes in these processes. Recently, observations from the James Webb Space Telescope have revealed impressive details about the quasar PJ308-21a fascinating example of these powerful objects. This quasar is located at a redshift of z = 6.2342corresponding to a time when the Universe was less than a billion years old. The redshift is a measure of this distance and the redshift of its light caused by the expansion of the Universe. In simple terms, this means that the quasar PJ308-21 is located at a very great distance from usso far away that we see it as it was when the cosmos was still very young. The Near Infrared Spectrograph (NIRSpec) captured the spectrum of this quasar with unprecedented precision: an uncertainty of less than 1% per pixel. This means that the measurements of the light and elements present in the quasar are extremely reliable and detailed with a very small margin of error.
What did the researchers discover?
These observations have allowed astronomers to make very precise analyses of the composition and properties of the quasar and surrounding galaxies. The host galaxy of PJ308-21 has a high metallicity and photoionization conditions typical of an active galactic nucleus (AGN) where the intense light from the quasar ionizes the surrounding gas. In contrast, one of the satellite galaxies has low metallicityindicating photoionization induced by star formation. With higher metallicity, the second satellite galaxy is partially photoionized by the quasarThese observations then allowed astronomers to determine the mass of the supermassive black hole at the center of the system which rises to about two billion solar massesThe results confirm that the quasar and surrounding galaxies are highly evolved in terms of mass and metal enrichment, and continue to grow significantly. These findings therefore provide new insights into the cosmic history and chemical evolution of galaxies, highlighting the importance of current research.
Map of hydrogen (red and blue) and oxygen (green) line emission in the PJ308-21 system, displayed 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 they contain. Credits: Decarli/INAF/A&A, 2024
The Transformative Impact of the James Webb Telescope
The data were obtained within the framework of the 1554 program, led by Decarli, one of the nine Italian projects of the first JWST observation cycle. The observations were carried out in integral field spectroscopy mode, which allowsstudy different gas tracers with a 3D approach. Using this technique, the team detected emissions from different elements, which are used to study the properties of the ionized interstellar medium, including the source and hardness of the photoionizing radiation field, metallicity, dust obscuration, electron density and temperature, and star formation rate. Federica Loiacono, an astrophysicist and postdoctoral fellow at INAF, highlights the importance of NIRSpec’s capabilities for study the properties of the gas around the black hole and in surrounding galaxies. She explains : ” Thanks to NIRSpec, we can for the first time study the optical band in the PJ308-21 system, rich in data on the properties of the gas near the black hole in the galaxy hosting the quasar and in the surrounding galaxies. This advance made it possible to compare the emission of hydrogen atoms with the chemical elements produced by the stars, thus establishing the richness in metals of the observed galaxies.. » With its unmatched capabilities, the JWST thus makes it possible to obtain observations of unprecedented precision in the distant Universe. data on metal enrichment, once out of reach at such distances, can now be mapped in detail in just a few hours of observation. This opens up new avenues for understanding the chemical evolution of galaxies, even at a time when the Universe was still young.
