"Our radiation-hydrodynamic simulations track both how gas falls onto the black hole and how the radiation it produces affects its surroundings," said Pacucci. "This interaction naturally creates an extremely dense environment that absorbs high-energy radiation and reprocesses it into the ultraviolet and optical light, which JWST observes after it is redshifted into the infrared. When we turn these simulations into mock observations, they match JWST data on Little Red Dots incredibly well, showing that their properties can be explained by well-understood physical processes in the early universe."
They found that their simulations reproduced the specific characteristics of LRDs, including their weak X-ray emission, the presence of metal and high-ionization lines, the absence of star-formation features, their abundance and redshift evolution, and their long-lived radiation-pressure-driven variable phases. Similarly, the presence of dense gas clouds surrounding the black holes also accounted for their extremely compact nature and why they appear overmassive relative to any stellar components.
Said Pacucci, "All the puzzling properties of the LRDs are explained within a single, self-consistent framework, without requiring any ad-hoc assumptions. What makes our model especially powerful is its simplicity, built on decades of theoretical work showing how direct collapse black holes are expected to form and evolve over cosmic time. One of JWST's primary scientific goals is to identify the first black holes and uncover how they formed.
"Astronomers have been searching for these primordial objects for decades, but direct evidence has remained elusive. Our results suggest that JWST is witnessing exactly this long-sought phase: the formation and growth of massive black hole seeds through direct collapse. This would be a major breakthrough, showing that the earliest black holes formed efficiently and early, and that JWST is finally opening a direct observational window onto their birth."
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