Roaming black holes may tell the hidden history of galaxies

Yale astronomers have found that black holes can wander far from their original locations, away from the centers of galaxies. The study, published in The Astrophysical Journal Letters, shows that wandering black holes may help reveal the history of galaxies. The researchers used a cosmological simulation called ASTRID to track black holes in galaxies with varying masses. They found that smaller galaxies retain information about their initial "seed" population, even after billions of years. The simulation showed that the number of galaxies with wandering black holes increased, while those with centered black holes decreased. This suggests that wandering black holes may be key to understanding how the first black holes formed. The findings offer a framework for a more comprehensive approach to finding and understanding the origin of black holes, including deep X-ray observations, optical and infrared spectroscopy, and radio measurements. Black holes are described as "remarkable cosmic archivists" that preserve a record of how their galaxies were assembled. The study highlights the importance of considering both centered and wandering black holes when studying the origins and dynamics of massive black holes and their host galaxies.

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