Black Holes Found Halting Star Formation in Galaxies

Bengaluru: A landmark study by astronomers at the Indian Institute of Astrophysics (IIA) has uncovered how supermassive black holes at galaxy centers can actively halt the birth of new stars, reshaping our understanding of galaxy evolution.

Tracing its roots back to an observatory set up in 1786 in Madras and later moved to Kodaikanal in 1899, IIA has long been at the forefront of astronomical research in India. Now, leveraging cutting-edge observational techniques, the institute has shed light on one of the universe’s most puzzling processes.

The study focuses on active galactic nuclei (AGN) — extremely energetic cores of galaxies powered by matter falling into supermassive black holes millions of times the Sun’s mass. These regions emit intense radiation and, in many cases, high-speed jets that can dramatically influence their surroundings.

Professor C S Stalin, co-author of the study, explained that new instrumentation like integral field spectroscopy has made this research possible. “These tools allow us to probe regions on very small scales that conventional imaging could not resolve, letting us explore the complex connection between AGN and their host galaxies,” he said.

The team analyzed a sample of 538 AGN, combining optical data from the Sloan Digital Sky Survey (SDSS) with radio observations from the Very Large Array (VLA). This multi-wavelength approach revealed clear patterns: radiation and jets from black holes can drive powerful outflows of gas, effectively depriving galactic centers of the raw material needed to form stars.

Lead researcher Payel Nandi emphasized the scale and depth of the study. “Previous research looked at individual galaxies or small samples. By analyzing hundreds of AGN systematically, we uncovered strong trends linking black hole activity, gas outflows, and the suppression of star formation,” she said.

The findings show that high-speed gas outflows are more than twice as common in galaxies with detectable radio emissions (56%) compared to those without (25%). This suggests that black hole-driven feedback plays a major role in regulating the growth and evolution of galaxies.

“This study gives us a clearer picture of why some galaxies stop forming stars while others continue to thrive,” Nandi added. The research also highlights the importance of combining data across multiple wavelengths to fully understand the forces shaping galaxies.