Fundamental Reference AGN Monitoring Experiment (FRAMEx). I. Jumping Out of the Plane with the VLBA

Abstract

We present the first results from the Fundamental Reference active galactic nucleus (AGN) Monitoring Experiment, an observational campaign dedicated to understanding the physical processes that affect the apparent positions and morphologies of AGNs. In this work, we obtained simultaneous Swift X-ray Telescope and Very Long Baseline Array (VLBA) radio observations for a snapshot campaign of 25 local AGNs that form a volume-complete sample with hard X-ray (14–195 keV) luminosities above 1042 erg s−1, out to a distance of 40 Mpc. Despite achieving an observation depth of ∼20 μJy, we find that 16 of 25 AGNs in our sample are not detected with the VLBA on milliarcsecond (subparsec) scales, and the corresponding core radio luminosity upper limits are systematically below predictions from the Fundamental Plane of black hole activity. Using archival Jansky Very Large Array (VLA) radio measurements, our sample jumps back onto the Fundamental Plane, suggesting that extended radio emission is responsible for the apparent correlation between radio emission, X-ray emission, and black hole mass. We suggest that this discrepancy is likely due to extranuclear radio emission produced via interactions between the AGN and host environment. We compare VLBA observations of AGNs to VLA observations of nearby Galactic black holes, and we find a mass-independent correlation between radio and X-ray luminosities of black holes of / ∼10−6, in line with predictions for coronal emission, but allowing for the possibility of truly radio-silent AGNs.

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“…While jetted AGN and low/hard XRBs clearly lie on the same FPBHA (Merloni et al 2003;Falcke et al 2004), Gültekin et al (2019), by including radio-active high-/soft-state XRBs, cannot rule out that the latter and Seyferts are inconsistent with the FP made up of low-/hard-state XRBs and LINERs. Furthermore, Fischer et al (2021) have recently shown that, Seyferts, once resolved with the VLBI on sub-parsec scales, can have corresponding L core upper limits that are systematically below the predictions from the FPBHA. The tension with the analogies between stellar-mass BHs and active SMBHs probably rests on attempting to use the optical class to set the association.…”

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“…However, this means-again-that the plane is no more probing the disk-jet coupling. Many other works underlined these and other flaws [see (Chiaberge, 2007;Foschini, 2014;Saikia et al, 2018;Berton et al, 2019a;Fischer et al, 2021), just to cite a few]. Nevertheless, these types of fundamental planes are still luring researchers, because of their ease.…”

Central X-ray point-sources found to be abundant in low-mass, late-type galaxies predicted to contain an intermediate-mass black hole

“…The "fundamental plane of black hole activity" for black holes with low accretion rates (Merloni et al 2003;Falcke et al 2004;Fischer et al 2020) encompasses stellar-mass black hole X-ray binaries and AGN, and enables one to estimate the black hole mass based upon the nuclear radio emission, L R = νL ν erg s −1 (at 5 GHz), and the unabsorbed nuclear X-ray luminosity, L X erg s −1 (at 0.5-10 keV). Although, it is noted that some AGN are X-ray luminous but radio silent (Radcliffe et al 2021).…”