Four 'Little Red Dot' pairs hint at black hole mergers in early universe

Four pairs of "Little Red Dots" (LRDs) were discovered in infrared images from the James Webb Space Telescope, suggesting that these objects may be black holes merging in the early universe. The research team, led by Takumi Tanaka of The University of Tokyo Kavli Institute for the Physics and Mathematics of the Universe, identified four sets of dual LRDs, each pair extremely close to each other, in the universe approximately 12.5–12.8 billion years ago. The distance between the two celestial bodies ranged from a few thousand to a few tens of thousands of light-years, much smaller than the Milky Way's 100,000-light-year diameter. The discovery implies that black holes in the early universe were growing rapidly, possibly through mergers, and that these mergers could be detected by future gravitational-wave observatories. The researchers used a new pixel-by-pixel color selection method to distinguish the two LRDs from other objects, which had previously been difficult due to the complexity of the images.

The study found that the four pairs of LRDs are not randomly distributed but exhibit a strong clustering on a scale of several thousand light-years. This clustering suggests that the LRDs are not just random objects but are part of a larger structure that may be linked to galaxy mergers. The researchers believe that the merging of black holes could be a mechanism by which gas is transported toward galaxy centers, driving matter toward the black hole. The results could indicate that galaxy mergers are linked to the rapid growth of black holes in the early universe. If each LRD contains a growing black hole, the black holes themselves might eventually merge as well. The next step for the researchers is to analyze the dual LRDs further and improve their method using a larger sample.

The study was published in the Publications of the Astronomical Society of Japan, and the findings are based on high-resolution infrared images from the James Webb Space Telescope. The research team used a new image analysis method to identify the LRDs, which were previously difficult to detect due to the complexity of the images. The discovery of these pairs provides insight into the formation and evolution of black holes in the early universe and suggests that mergers may play a significant role in their growth.

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