A new fundamental plane for radiatively efficient black-hole sources

Abstract

In recent years, it was found that there are several low/hard state of X-ray binaries (XRBs) follow an `outliers' track of radio--X-ray correlation ($L_{\mathrm{R}}\propto L_{\mathrm{X}}^b$ and $b\sim 1.4$), which is much steeper than the former universal track with $b\sim 0.6$. In this work, we compile a sample of bright radio-quiet active galactic nuclei (AGNs) and find that their hard X-ray photon indices and Eddington ratios are positively correlated, which is similar to that of `outliers' of XRBs, where both bright AGNs and `outliers' of XRBs have bolometric Eddington ratios $\gtrsim 1$ ($L_{\mathrm{Edd}}$ is Eddington luminosity). The Eddington-scaled radio--X-ray correlation of these AGNs is also similar to that of `outliers' of XRBs, which has a form of $L_{5GHz}/L_{\mathrm{Edd}}\propto (L_{2-10keV}/L_{\mathrm{Edd}}{)}^c$ with $c\simeq 1.59$ and 1.53 for AGNs and XRBs respectively. Both the positively correlated X-ray spectral evolution and the steeper radio--X-ray correlation can be regulated by a radiatively efficient accretion flow (e.g., disk-corona). Based on these similarities, we further present a new fundamental plane for `outliers' of XRBs and bright AGNs in black-hole (BH) mass, radio and X-ray luminosity space: $\log L_{\mathrm{R}}=1.59_{-0.22}^{+0.28}\log L_{\mathrm{X}}-0.22_{-0.20}^{+0.19}\log M_{\mathrm{BH}}-28.97_{-0.45}^{+0.45}$ with a scatter of ${\sigma }_{\mathrm{R}}=0.51\mathrm{dex}$. This fundamental plane is suitable for radiatively efficient BH sources, while the former plane proposed by Merloni et al. and Falcke et al. may be most suitable for radiatively inefficient sources.

Accepted for publication in ApJ Letter; emulateapj format; 6 pages, 3 figures, 1 table

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• Limits on luminosity and mass accretion rate of a radiation pressure dominated accretion disc
• The X-ray emission in young radio AGNs
• A universal scaling law of black hole activity including gamma-ray bursts
• Constraints on the radio loud/radio quiet dichotomy from the fundamental plane
• Hard - X-rays selected Active Galactic Nuclei. I. A radio view at high-frequencies
• A toy model for X-ray spectral variability of active galactic nuclei
• The MEXSAS2 Sample and the Ensemble X-ray Variability of Quasars
• Correlations of Disk and Jet Emission Deviating from the Fundamental Plane