New Delhi, July 6: Astronomers have uncovered a hidden population of weakly active supermassive black holes in nearby galaxies using high-resolution radio observations, offering new insights into how galaxies evolve over time.
The discovery, announced by the Government of India on Monday, is based on an international study involving researchers from the Indian Institute of Astrophysics (IIA), Bengaluru, an autonomous institute under the Department of Science and Technology (DST).
The research team, including Dr. Aru Beri of IIA, used the e-MERLIN radio telescope array in the United Kingdom to observe 280 nearby galaxies selected from the Palomar sample. The survey focused on the central regions of galaxies at extremely high resolution, enabling astronomers to detect faint radio emissions from supermassive black holes that had previously remained undetected.
The study found compact radio emissions in nearly one-quarter of the galaxies surveyed, indicating the presence of weakly accreting supermassive black holes. While most of the detected sources appeared highly compact, some exhibited jet-like radio structures extending several parsecs from the galactic centre.
Astronomers said almost every galaxy is believed to host a massive black hole at its core, but many remain extremely faint and difficult to identify using conventional observation techniques. Detecting these hidden black holes is important because they can influence star formation and the long-term evolution of galaxies by releasing energy through jets and outflows.
To confirm the findings, the researchers combined the radio observations with X-ray data from NASA’s Chandra X-ray Observatory. The multi-wavelength analysis established that the detected emissions originated from actively accreting supermassive black holes rather than from stellar processes such as star formation, supernova remnants or X-ray binary systems.
According to the researchers, the findings suggest that faint, low-level black hole activity may represent the dominant mode of black hole growth in the present-day Universe. They also highlighted the importance of high-resolution radio astronomy in identifying weakly active black holes that often escape detection in conventional galaxy surveys.
The study is among the first statistically complete high-resolution radio surveys capable of systematically identifying faint black hole activity in nearby galaxies. Unlike previous studies, which were either limited by sensitivity or focused on smaller galaxy samples, the new survey provides a broader and more accurate picture of black hole activity in the local Universe.
The research has been published in the scientific journal Monthly Notices of the Royal Astronomical Society and was led by D. R. A. Williams-Baldwin along with an international team of collaborators, including Dr. Aru Beri from the Indian Institute of Astrophysics. (PIB)
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