Radio Properties of Swift-BAT AGNs: Insights from SKA Pathfinder Surveys

Abstract

Active galactic nuclei (AGNs) are among the most powerful sources in the Universe, with their X-ray and radio emissions revealing the physics of black hole accretion and jet processes. We investigate the radio properties of Seyfert galaxies selected from the Swift-BAT 70-month hard X-ray survey, using radio observations from VLASS and RACS. From a parent sample of 752 unbeamed AGNs, we compile 604 Seyfert galaxies with measurements of radio luminosity, X-ray luminosity, and black hole mass. The sample spans X-ray Eddington ratios LX/LEdd from 10−7.5 to 1, with most sources ≳ 10−4. We first characterise the distribution of the X-ray–radio loudness, finding a broad, continuous range spanning about 4 orders of magnitude, with no clear evidence for a bimodal separation between radio-quiet and radio-loud populations. We also revisit the fundamental plane (FP) in an Eddington-scaled form and quantify its dependence on optical type and radio morphology. Subsamples by Seyfert type show consistent FP relations within uncertainties once a luminosity cut is applied, implying that optical classification does not significantly impact the radio–X-ray correlation. Radio morphology introduces secondary but systematic shifts, i.e., compact sources align with the FP for RIAF-dominated systems with compact jets, while extended and jet-like morphologies display excess radio luminosity at fixed LX/LEdd. This possibly reflects additional contributions from jets and/or star formation. We further discuss the implications for AGN unification, noting that orientation does not play a key role in shaping the FP.