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EI2GYB > ASTRO 05.10.25 13:51l 43 Lines 6477 Bytes #57 (0) @ WW
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Subj: Two Quasars From the Early Universe Provide Clues About Gal
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Two Quasars From the Early Universe Provide Clues About Galactic Evolution
One of the greatest accomplishments of the James Webb Space Telescope is the way it has allowed scientists to examine galaxies that existed when the Universe was very young. This is one of the major objectives that informed Webb's design, which was to provide high-resolution images of the earliest galaxies, allowing astronomers and cosmologists to gain a better understanding of how they have evolved over time. Intrinsic to this is the study of early massive black holes that have since evolved into the supermassive black holes (SMBHs) that reside at the centers of galaxies today.
To the surprise of scientists, Webb's early observations revealed a population of galaxies and black holes that appeared significantly larger than previously predicted by cosmological models. This led to new theories on how galaxies and massive black holes could have formed so rapidly during the early Universe. In a recent study, an international team of researchers examined two galaxies with massive black holes at their centers that existed 12.9 billion years ago (over 1 billion years after the Big Bang). The study offers new insights into how these gravitational behemoths shaped the evolution of early galaxies.
The research was led by Masafusa Onoue and Xuheng Ding, an Assistant Professor at the Waseda Institute for Advanced Study (WIAS) and a Professor at Wuhan University (respectively). They and multiple team members are also researchers with the Kavli Institute for the Physics and Mathematics of the Universe (IMPU), and were joined by colleagues from the MIT Kavli Institute for Astrophysics and Space Research, the Research Center for Space and Cosmic Evolution, the Cosmic Dawn Center (DAWN), the Max Planck Institute for Astronomy, the Max Planck Institute for Astrophysics, the National Astronomical Observatory of Japan (NAOJ), JAXA, and multiple institutes universities worldwide.
Starting in the 1950s, scientists began making a series of discoveries that would lead them to realize that massive galaxies contained SMBH at their centers. This was first suggested by the discovery of bright radio sources in the cosmos that were named "quasi-stellar objects" (quasars for short). Further observations of these objects revealed that they were actually the core regions of galaxies that were particularly bright, leading to the term Active Galactic Nuclei (AGN). From the 1970s onward, scientists determined that extremely compact objects were at the center of AGNs that were black holes between a hundred thousand to several hundred billion solar masses.
By studying quasars, astronomers can identify distant galaxies in the night sky and learn more about how their shapes and behavior have evolved over time. Observations of those that are close to our galaxy have shown a strong link between the mass of the galaxy and its central black hole, suggesting that they evolve in tandem (or co-evolve). Despite all that we have learned about galaxies and their SMBHs, there are still unresolved questions regarding the relationship between the two and how it came to be. Hence why astronomers have been eager to observe galaxies as they existed during the early Universe (less than 1 billion years after the Big Bang).
For their study, the team focused on two quasars, J2236+0032 and J1512+442, two of the farthest known quasars that were originally identified by the Subaru Telescope in Hawaii as part of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). They have since been subjected to follow-up observations using the JWST's Near Infrared Spectrograph (NIRSpec) during its year of operations. The NIRSpec data revealed that the parent galaxies had already grown to approximately 40 to 60 billion solar masses by about 12.9 billion years ago, which is extremely rapid considering the Universe was only 800 million years old.
This came as a surprise, as previous research has shown that SMBHs suppress the growth of host galaxies by arresting star formation, a process known as "quenching." It was believed that this is what caused "starburst" galaxies, which experience intense rates of star formation, to transition into becoming "quiescent." "It was totally unexpected to find such mature galaxies in the Universe less than a billion years after the Big Bang," Onoue said in an IMPU press release. "What is even more remarkable is that these 'dying' galaxies still host active supermassive black holes."
These findings are especially significant, as they capture the role that SMBHs played in the evolution of the fastest-growing galaxies that existed during the early Universe. They also offer insight into the growth history of galaxies, which could shed light on some of the other mysteries in our current cosmological models, such as Dark Matter and Dark Energy. Looking ahead, the team will continue their analysis of the JWST data and hope to conduct additional observations to learn more about the dynamics of SMBHs and their host galaxies during the early Universe.
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