A significant discovery by astronomers at the Indian Institute of Astrophysics (IIA) has revealed that the activity surrounding supermassive black holes can effectively inhibit the formation of new stars within their host galaxies. This research, conducted by scientists based in Bengaluru, builds on the institute”s long history, which dates back to an observatory established in 1786 in Madras, later relocated to Kodaikanal in 1899.
According to Prof C S Stalin, a faculty member at IIA and a co-author of the research, advancements in observational astronomy have enabled this groundbreaking study. “Recent improvements in instrumentation, such as integral field spectroscopy, allow us to explore regions at very small scales that were previously unresolvable by conventional imaging techniques,” he explained in an interview.
The active galactic nuclei (AGN), which are energetic centers of galaxies emitting significant radiation and, in some cases, powerful jets, are fueled by matter falling into supermassive black holes that can be millions of times more massive than the Sun.
Lead author Payel Nandi, a Ph.D. student at IIA, stated that the research has demonstrated how the intense radiation emitted from around these black holes and the high-speed jets can together expel gas from the central regions of galaxies, thereby potentially halting star formation and regulating the growth of galaxies.
Nandi highlighted the uniqueness of the study, noting its extensive scale and depth of analysis. “We examined 538 AGN, conducting a systematic comparison of both optical and radio properties, which revealed trends connecting black hole activity, gas outflows, and suppression of star formation,” she remarked.
The researchers integrated optical data from the Sloan Digital Sky Survey (SDSS) with radio data from the Very Large Array (VLA) in the United States, a process that required nearly four months for data analysis and cross-matching. The results were recently published in The Astrophysical Journal.
Nandi emphasized the importance of this work for future research, as it sheds light on one of astronomy”s enduring mysteries: why some galaxies cease to form stars while others continue to thrive. To fully comprehend galaxy evolution, astronomers must analyze data across various wavelengths—optical, radio, and beyond.
This multifaceted 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 enhancing theoretical models and simulations regarding galaxy evolution.
The researchers concluded that the primary driver of energetic gas outflows is the radiation emitted from black holes. “These outflows, characterized by rapid streams of gas expelled from galactic centers, are observed to be more than twice as common in galaxies that show radio emissions compared to those that do not,” Prof Stalin noted.
He further asserted that this study contributes a crucial piece to the puzzle of galaxy evolution, enhancing understanding of how black holes influence the cosmic landscape. “This comprehensive and data-driven research provides a strong foundation for future investigations into the role of black holes in shaping galaxies,” Nandi added.
