IIA astronomers’ groundbreaking study confirms black hole activity suppresses the birth of new stars

Astronomers at the Indian Institute of Astrophysics have discovered that radiation and jets from supermassive black holes suppress star formation in galaxies. Studying 538 active galactic nuclei using optical and radio data, the team confirmed black hole activity regulates galactic evolution and growth

Chennai/Bengaluru: A groundbreaking investigation by astronomers of the Indian Institute of Astrophysics (IIA) has confirmed that activity around supermassive black holes can suppress the birth of new stars in their host galaxies.

Bengaluru-based IIA, an autonomous institute of the Department of Science and Technology (DST), traces its origins back to an observatory set up in 1786 in Madras, which in 1899, moved to Kodaikanal.

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Prof CS Stalin, a faculty member at IIA and co-author of the study, said the study has been possible because of the recent advancements in observational astronomy.

“Because of advancements in instrumentation, such as the integral field spectroscopy, we are able to probe regions on very small scales that were not possible a few years ago. These were not resolvable by conventional imaging techniques. And because these observations are available now, we are able to probe the complex connection between active galactic nuclei (AGN) and their host galaxies,” Prof Stalin said.

AGN, he explained, are energetic galaxy centres that emit copious radiation and, in some cases powerful relativistic jets. They are powered by matter falling onto supermassive black holes, many millions of times more massive than the Sun.

Payel Nandi, a Ph D. student at IIA and the lead author of the study, said they have now proved that the intense radiation from around the black holes and the high-speed jets they emit can work together to eject gas from the centres of galaxies, potentially shutting down star formation in their central regions, thereby regulating galactic growth.

According to her, what makes the study truly unique is the scale and the depth of its analysis. Previous research works have focused on individual galaxies or small samples.

“We studied 538 AGN. We carried out a systematic comparison of optical and radio properties, which led us to uncover trends linking black hole activity, gas outflows and star formation suppression,” Nandi said.

The researchers said they combined optical data from the Sloan Digital Sky Survey (SDSS) with radio data from the Very Large Array (VLA). Both SDSS and VLA are located in the United States of America.

The analysis and data cross-matching took them nearly four months, added the researchers, who published the study recently in ‘The Astrophysical Journal’.

“This work is important for future studies because it helps scientists understand one of the biggest mysteries in astronomy: why some galaxies stop forming stars while others continue to flourish,” added Nandi.

The findings also show that to fully understand how galaxies evolve, astronomers must combine data across multiple wavelengths — optical, radio and beyond, said Nandi.

“This approach reveals not just what we see as light, but also the hidden forces and energetic processes that govern how galaxies live and die. Such insights are crucial for improving theoretical models and computer simulations of galaxy evolution,” she added.

Key takeaway from the study, said the researchers, is that radiation from black holes is the main driver of energetic gas outflows.

“Such outflows, which are high-speed streams of gas pushed out from galactic centres, are more than twice as likely in galaxies detected in radio wavelengths (56 per cent) compared to those without radio emission (25 per cent),” added Prof Stalin.

He added that the study has put in place a key piece of the puzzle that will help astronomers to eventually understand the full picture of galaxy evolution.

“This comprehensive and data-driven study lays a strong foundation for future explorations of how black holes shape the cosmic landscape,” added Nandi.