Much of a sample of the mysterious distant red objects that the James Webb Space Telescope, operated jointly by the European Space Agency, the Canadian Space Agency and NASA, revealed at its debut shows signs of containing growing supermassive black holes.
In December 2022, less than six months after beginning scientific operations, the Webb telescope revealed something never before seen: numerous small-looking red objects in the sky, which scientists soon called “small red dots” (LRD, by its acronym in English). Although these points are quite abundant, researchers are stumped by their nature, the reason for their unique colors and what they convey about the early universe.
A team of astronomers recently collected one of the largest LRD samples to date, almost all of which existed during the first 1.5 billion years after the Big Bang. They found that a large fraction of the LRDs in their sample showed signs of containing growing supermassive black holes.
“We are baffled by this new population of objects that Webb has discovered. We don’t see analogs of them at lower redshifts, so we haven’t seen them before Webb,” Dale Kocevski of Colby College in Waterville, and lead author of the study published on the arXiv preprint server, said in a statement. »A substantial amount of work is being done to try to determine the nature of these small red dots and whether their light is dominated by accreting black holes«.
One factor that significantly contributed to the team’s large LRD sample size was their use of publicly available Webb data. To start, the team searched for these red sources in the Cosmic Evolution Early Release Science (CEERS) survey before expanding their scope to other extragalactic legacy fields, including the JWST Advanced Deep Extragalactic Survey (JADES) and the Proxima Deep Extragalactic Public Exploratory Survey. Generation (NGDEEP).
The methodology used to identify these objects also differed from previous studies, resulting in the census covering a wide range of redshifts. The distribution they discovered is intriguing: LRDs emerge in large numbers around 600 million years after the Big Bang and experience a rapid decline in quantity around 1.5 billion years after the Big Bang.
The team sought spectroscopic data on some of the LRDs in their sample in the Red Unknowns: Bright Infrared Extragalactic Survey (RUBIES) study. They found that about 70% of the targets showed evidence of gas orbiting fast at 2 million miles per hour (1,000 kilometers per second), a sign of an accretion disk around a supermassive black hole. This suggests that many LRDs are black holes in the process of accretionalso known as active galactic nuclei (AGN).
«The most exciting thing for me is the redshift distributions. These really red, high redshift sources basically cease to exist at a certain point after the big Bang“said Steven Finkelstein, co-author of the study at the University of Texas at Austin. »If they are growing black holes, and we believe that at least 70% of them are, this indicates an era of hidden black hole growth in the early universe«.
The team’s research supports the argument that much of the light coming from these objects comes from accreting black holes and not from stars. Fewer stars means smaller, lighter galaxies that can be understood by existing theories.
“This is how you solve the problem of the destruction of the universe,” said Anthony Taylor, a co-author of the study at the University of Texas at Austin.
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