High-resolution radio study reveals faint black hole activity in nearby galaxies

New Delhi, July 6 (IANS) An international team containing an Indian astronomer used the e‑MERLIN radio array to detect compact radio emission from the centres of nearly one‑quarter of 280 nearby galaxies, and revealed a hidden population of weakly accreting supermassive black holes, an official statement said on Monday.

Dr. Aru Beri from the Indian Institute of Astrophysics (IIA), an autonomous institution under the Department of Science and Technology (DST), used the e-MERLIN radio array, and observed nearby galaxies selected from the Palomar sample and probed their central regions on parsec scales.

These newly discovered weakly accreting supermassive black holes are often missed in conventional observations, the statement from the Ministry of Science & Technology said.

The researchers detected compact radio emission from the centres of nearly one-quarter of the galaxies, revealing the presence of weakly accreting supermassive black holes that are often missed in conventional observations.

Most detected sources appear extremely compact, while a smaller fraction shows jet-like radio structures extending over several parsecs.

Hunting these black holes is essential as they can inject energy into their surroundings through jets and outflows, influencing star formation rates and the long-term evolution of galaxies.

Astronomers believe that almost every galaxy harbours a massive black hole at its centre. However, many of these black holes remain extremely faint and spotting them was a challenge, the statement noted.

The study represents one of the first statistically complete high-resolution radio surveys capable of isolating faint black hole activity in nearby galaxies.

Earlier studies either lacked the sensitivity and angular resolution needed to separate weak nuclear emission from surrounding stellar activity or focused on smaller and potentially biased galaxy samples, the ministry said.

To strengthen these findings, the radio observations were complemented with X-ray data from NASA’s Chandra X-ray Observatory.

The results suggest that faint, low-level black hole activity may represent the dominant mode of black hole growth in the present-day Universe.

The study also highlighted the importance of high-resolution radio observations in revealing a population of weakly active black holes that often remain hidden in conventional galaxy surveys.

—IANS

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