Did Primordial Black Holes Seed the Universe’s Earliest Galaxies?

A new study suggests that primordial black holes (PBHs) may explain the early appearance of Active Galactic Nuclei (AGNs) in the Universe. These bright cosmic objects have been detected as far back as redshift 10-10.4, a time when the Universe was still in its infancy. Researchers now propose that PBHs could have seeded these ancient galaxies, leaving a detectable mark on the early Universe's evolution.

The research focuses on how PBH-seeded galaxies might have influenced the global 21-cm signal—a key tracer of the Universe's first billion years. By incorporating these galaxies into existing models, scientists found that their presence could significantly alter predictions for this signal. The team used a standard ΛCDM cosmological model, adjusting parameters to fit current observations.

An analytical model of PBHs, constrained by known astrophysical limits, formed the basis of the study. The findings suggest that AGNs, if seeded by PBHs, would have played a major role in shaping the 21-cm signal. This adjustment provides a more complete picture of the early Universe's conditions. The work also introduces a new way to interpret future 21-cm observations. By accounting for PBH-seeded galaxies, researchers aim to uncover details about the first luminous epochs. This approach could help distinguish between different theories of early galaxy formation.

The study highlights the potential impact of PBH-seeded AGNs on the 21-cm global signal. These modifications could improve our understanding of the Universe's early structure. Future observations may now include these findings to refine models of cosmic dawn.