High-resolution e-MERLIN radio observations of 280 nearby galaxies from the Palomar sample identified compact radio emission in about 25% of targets, marking a hidden population of faint, weakly accreting supermassive black holes; results published in MNRAS and cross-checked using Chandra X-ray data.
Survey and instruments
- e-MERLIN array: network of seven UK radio telescopes providing milli-arcsecond to sub-arcsecond resolution for parsec-scale imaging.
- Sample: 280 nearby galaxies selected from the Palomar sample, observed on parsec scales for nuclear radio emission.
- X-ray cross-match: Chandra X-ray Observatory data used to confirm accretion-related nuclear activity.
Key findings
- Detection rate: compact radio cores detected in ≈25% of galaxies, consistent with weakly accreting SMBHs.
- Morphology: most detections are extremely compact; a minority show jet-like structures extending several parsecs.
- Observational gap: many faint nuclei are missed by conventional surveys without high-resolution radio data.
Astrophysical implications
- SMBH growth mode: low-level, faint accretion may be the prevalent growth channel for black holes in the local Universe.
- Feedback: jets and outflows from faint AGN can inject energy into galactic centres and influence nuclear star formation.
IASPOINT Booster Facts
- Publication: Monthly Notices of the Royal Astronomical Society (July 2026).
- Indian involvement: team includes researchers from the Indian Institute of Astrophysics; supported by India’s Department of Science and Technology.
- Parsec conversion: 1 parsec ≈ 3.26 light-years.
- Palomar sample: a standard nearby-galaxy optical spectroscopic sample used for nuclear-activity studies.