A groundbreaking study conducted by astronomers at the Indian Institute of Astrophysics has revealed that the activity surrounding supermassive black holes plays a significant role in suppressing the formation of new stars within their host galaxies. The research focused on 538 active galactic nuclei, utilizing both optical and radio data to establish that black hole activity is a key regulator of galactic evolution and growth.
Located in Bengaluru, the Indian Institute of Astrophysics is an autonomous institution under the Department of Science and Technology. Its roots trace back to a 1786 observatory in Madras, which relocated to Kodaikanal in 1899. Professor CS Stalin, a faculty member at the institute and co-author of the research, noted that recent advancements in observational astronomy enabled their findings. He stated, “Due to improvements in instrumentation, such as integral field spectroscopy, we can now explore regions on extremely small scales that were previously unresolvable with conventional imaging techniques.”
According to Prof Stalin, active galactic nuclei (AGN) are powerful centers within galaxies that emit significant radiation and, in certain instances, generate strong relativistic jets. These phenomena are fueled by matter accreting onto supermassive black holes, which can be millions of times more massive than the Sun.
Lead author and Ph.D. student Payel Nandi explained that their research has demonstrated how the intense radiation emitted by black holes, along with the high-speed jets, can eject gas from the central regions of galaxies. This process may effectively halt star formation, thereby influencing the growth of galaxies.
Nandi emphasized the unique nature of their study, highlighting the scale and depth of their analysis. Previous investigations often concentrated on individual galaxies or limited samples. “Our study examined 538 AGN and involved a systematic comparison of optical and radio properties, which allowed us to uncover trends connecting black hole activity, gas outflows, and the suppression of star formation,” she said.
The researchers combined optical data from the Sloan Digital Sky Survey (SDSS) with radio data from the Very Large Array (VLA), both located in the United States. The cross-matching and analysis of this data took nearly four months. Their findings were recently published in The Astrophysical Journal.
Nandi remarked on the significance of their work for future studies, as it sheds light on one of astronomy”s longstanding mysteries: why certain galaxies cease star formation while others continue thriving. She added that to fully grasp galactic evolution, astronomers must analyze data across multiple wavelengths, including optical and radio.
This comprehensive approach not only reveals visible light but also uncovers the hidden forces and energetic processes that dictate the life cycles of galaxies. Such insights are vital for refining theoretical models and enhancing computer simulations of galaxy evolution.
A key takeaway from the study is that radiation from black holes significantly drives energetic gas outflows. The researchers found that these high-speed gas streams are more than twice as likely to occur in galaxies detected through radio wavelengths (56 percent) compared to those without radio emissions (25 percent).
Prof Stalin concluded that this study contributes a crucial piece to the puzzle of understanding galaxy evolution. “This comprehensive and data-driven investigation lays a solid foundation for future explorations into how black holes shape the cosmic landscape,” added Nandi.
