An international team, including Indian astronomer Dr. Aru Beri from the Indian Institute of Astrophysics, utilized the e-MERLIN radio array to identify compact radio emissions from the centers of about 25% of 280 nearby galaxies. These emissions unveiled a concealed group of weakly accreting supermassive black holes, as confirmed by the Ministry of Science & Technology. The newly discovered black holes, often overlooked in standard observations, were found in galaxies selected from the Palomar sample and examined on parsec scales.
The researchers noted that the majority of the detected sources exhibited extreme compactness, with some displaying jet-like radio structures extending across multiple parsecs. It is crucial to track these black holes as they can release energy into their surroundings through jets and outflows, impacting star formation rates and the overall evolution of galaxies. While it is widely believed that nearly every galaxy houses a massive black hole at its core, many of these black holes are dim and challenging to detect, the statement emphasized.
This study, considered one of the first comprehensive high-resolution radio surveys, is adept at singling out faint black hole activities in nearby galaxies. Previous studies either lacked the necessary sensitivity and angular resolution to differentiate weak nuclear emissions from surrounding stellar activities or focused on smaller and potentially biased galaxy samples, as highlighted by the ministry. To reinforce these discoveries, the radio observations were paired with X-ray data from NASA’s Chandra X-ray Observatory.
The findings indicate that faint, low-level black hole activities may represent the primary mode of black hole growth in the contemporary Universe. Moreover, the study underscores the significance of high-resolution radio observations in uncovering a cohort of weakly active black holes that are frequently concealed in traditional galaxy surveys.
