ALMA observation of an evolving magnetized corona in the radio-quiet changing-state active galactic nucleus NGC 1566
The origin of compact millimeter (mm) continuum emission from radio-quiet active galactic nuclei (RQAGNs) remains not fully understood. Changing-state AGNs (CSAGNs) exhibit rapid and strong variability, which allows us to investigate the origin of the mm emission. We present here the results of a first study of the mm continuum variability of a CSAGN using archival ALMA band 6 (∼230 GHz) observations of NGC 1566 obtained from 2014 to 2023. We find a positive correlation between the mm and X-ray flux with an intrinsic scatter of 0.05 dex (1 σ ), suggesting a common origin. The mm spectral index ( α mm ) is found to be in the range of 0.13±0.38 to −0.26±0.53, consistent with a compact optically thick synchrotron source. No significant correlation was found between the α mm and the mm flux. The mm/X-ray ratio also shows no clear link to the Eddington ratio but is higher in the low-accretion state. We discuss several scenarios about the origin of the mm emission in NGC 1566. We find that synchrotron emission in the magnetized X-ray corona appears to be the most probable origin of the mm emission, confirming that mm emission can be used as a tracer of AGN activity in RQAGNs.
Authors
- Arghajit Jana (ORCID: https://orcid.org/0000-0001-7500-5752)
- Mai Liao (ORCID: https://orcid.org/0000-0002-9137-7019)
- T. Kawamuro (ORCID: https://orcid.org/0000-0002-6808-2052)
- Cláudio Ricci (ORCID: https://orcid.org/0000-0001-5231-2645)
- Michael Koss (ORCID: https://orcid.org/0000-0002-7998-9581)
- F. E. Bauer (ORCID: https://orcid.org/0000-0002-8686-8737)
- Chin-Shin Chang (ORCID: https://orcid.org/0000-0001-9910-3234)
- Jacob S Elford (ORCID: https://orcid.org/0000-0002-6139-2226)
- Benny Trakhtenbrot (ORCID: https://orcid.org/0000-0002-3683-7297)
- Elena Shablovinskaya (ORCID: https://orcid.org/0000-0003-2914-2507)
- Yoshiyuki Inoue (ORCID: https://orcid.org/0000-0002-7272-1136)
- Sophie Venselaar
Institutions
- Space Science Institute (US)
- Tel Aviv University (IL)
- Kavli Institute for the Physics and Mathematics of the Universe (JP)
- University of Tarapacá (CL)
- Peking University (CN)
- Atacama Large Millimeter Submillimeter Array (CL)
- Pioneer (Japan) (JP)
- Kavli Institute for Theoretical Sciences (CN)
- RIKEN (JP)
- Eureka Scientific (US)
- Information and Mathematical Science and Bioinformatics (Japan) (JP)
- The University of Tokyo (JP)
- Universidad Diego Portales (CL)
- The University of Osaka (JP)
Publication Details
- Journal
- Astronomy and Astrophysics
- Published
- 2025-05-27
- DOI
- https://doi.org/10.1051/0004-6361/202554491
- Citations
- 1
- Primary Topic
- Stellar, planetary, and galactic studies
- Type
- article
- Field-Weighted Citation Impact
- 1.15
Funders
- National Science Foundation
- National Radio Astronomy Observatory
- European Commission
- Ministry of Education, Culture, Sports, Science and Technology
- Korea Astronomy and Space Science Institute
- National Astronomical Observatory of Japan
- Agencia Nacional de Investigación y Desarrollo
- National Science and Technology Council
- Japan Society for the Promotion of Science
- National Institutes of Natural Sciences