Researchers at Penn State have used forefront X-ray observations and supercomputer simulations to create a model of the growth of supermassive black holes in the centers of galaxies over 12 billion years. The team, led by astronomers Fan Zou and W. Niel Brandt, combined data from X-ray sky surveys and supercomputer simulations to track how supermassive black holes grow through accretion of cold gas and mergers with other black holes. The results of this research will be presented at the American Astronomical Society meeting in June 2024, with one paper already published in The Astrophysical Journal and another to be submitted.
Through their observations, the research team measured the growth of black holes from a sample of 1.3 million galaxies, containing over 8,000 rapidly growing black holes. By analyzing X-ray data from space telescopes such as the Chandra X-ray Observatory and the XMM-Newton, they were able to track the accretion-driven growth of black holes in galaxies. The data showed that more massive galaxies grew their black holes faster through accretion, indicating a strong correlation between galaxy mass and black hole growth.
Using supercomputer simulations from the IllustrisTNG project, the team was able to model the growth of black holes through mergers. They found that while accretion was the primary driver of black hole growth in most cases, mergers also played a significant role, particularly in the past 5 billion years. The total number of supermassive black holes in the universe was largely established by 7 billion years ago, with new black holes continuing to emerge earlier in the universe’s history. The research provides new insights into how black holes have evolved over cosmic time.
The hybrid approach taken by the researchers, combining observed growth by accretion with simulated growth through mergers, allowed for a comprehensive understanding of the growth history of supermassive black holes. This approach produced a more realistic picture of black hole growth up to the present day, highlighting the dynamic processes that drive the evolution of these cosmic behemoths. By studying the growth of supermassive black holes in the Milky Way and other galaxies, the team was able to trace the late growth of our own Galaxy’s central black hole.
The research team, which includes Zou and Brandt as well as other astronomers and statisticians from various institutions, received funding from the U.S. National Science Foundation, the Chandra X-ray Center, and Penn State. The sharing of simulation results from the IllustrisTNG project with the scientific community was instrumental in enabling this research. The findings provide valuable insights into the growth mechanisms of supermassive black holes and the role they play in shaping the evolution of galaxies over cosmic time. By combining cutting-edge observations with state-of-the-art simulations, the researchers have advanced our understanding of the growth of supermassive black holes in the universe. Overall, the research sheds light on the complex interplay between galaxy evolution, black hole growth, and cosmic history, deepening our knowledge of these fundamental astrophysical processes.
