Radio Observations of Four Active Galactic Nuclei Hosting Intermediate-mass Black Hole Candidates: Studying the Outflow Activity and Evolution
Journal article, 2022

Observational searches for intermediate-mass black holes (IMBHs; 102-106 M ⊙) include relatively isolated dwarf galaxies. For those that host active galactic nuclei (AGNs), the IMBH nature may be discerned through the accretion-jet activity. We present radio observations of four AGN-hosting dwarf galaxies, which potentially harbor IMBHs. Very large array (VLA) observations indicate steep spectra (indices of −0.63 to −1.05) between 1.4 and 9 GHz. However, a comparison with the 9 GHz in-band spectral index shows a steepening for GH047 and GH158 (implying older/relic emission) and flattening for GH106 and GH163 (implying recent activity). Overlapping emission regions in the VLA 1.4 GHz and our very long baseline array (VLBA) 1.5 GHz observations, and possibly symmetric pc-scale extensions, are consistent with recent activity in the latter two. Using the compact VLBA radio luminosity, X-ray luminosity (probing the accretion activity), and the black hole masses, all AGNs are found to lie on the empirical fundamental plane relation. The four AGNs are radio-quiet with relatively higher Eddington ratios (0.04-0.32) and resemble X-ray binaries during spectral state transitions that entail an outflow ejection. Furthermore, the radio to X-ray luminosity ratio log R X of −3.9 to −5.6 in these four sources support the scenarios that include corona mass ejection from the accretion disk and wind activity. The growth to kpc-scales likely proceeds along a similar trajectory to young AGNs and peaked spectrum sources. These complex clues can thus aid in the detection and monitoring of IMBHs in the nearby universe.

Author

Xiaolong Yang

Shanghai Astronomical Observatory

P. Mohan

Shanghai Astronomical Observatory

Jun Yang

Chalmers, Space, Earth and Environment, Onsala Space Observatory

Luis C. Ho

Beijing University of Technology

J. N.H.S. Aditya

ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D)

The University of Sydney

Shaohua Zhang

Shanghai Normal University

Sumit Jaiswal

Shanghai Astronomical Observatory

Xiaofeng Yang

Xinjiang Astronomical Observatory

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 941 1 43

Subject Categories

Subatomic Physics

Astronomy, Astrophysics and Cosmology

DOI

10.3847/1538-4357/ac9e9d

More information

Latest update

10/27/2023