A Study of the Accretion–Jet Coupling of Black Hole Objects at Different Scales

The fundamental plane of black hole activity is a very important tool to study accretion and jets. However, we found that the SEDs of AGNs and XRBs are different in the 2–10 keV energy band, and it seems inappropriate to use 2–10 keV X-ray luminosities to study the fundamental plane. In this work, we use the luminosity near the peak of the blackbody radiation of the active galactic nuclei and black hole binaries to replace the 2–10 keV luminosity. We re-explore the fundamental plane of black hole activity by using the 2500 A˚ luminosity as the peak luminosity of the blackbody radiation of AGNs and 1 keV luminosity as the peak luminosity of the blackbody radiation of XRBs. We compile samples of black hole binaries and active galactic nuclei with luminosity near the peak luminosity of blackbody radiation and study the fundamental plane between radio luminosity (LR), the peak luminosity of blackbody radiation (Lpeak), and black hole mass (MBH). We find that the radio–peak luminosity correlations are L5GHz/LEdd∝(L2500A˚/LEdd)1.55 and L5GHz/LEdd∝(L1keV/LEdd)1.53 for AGN and XRB, respectively, in the radiatively efficient sample, and L5GHz/LEdd∝(L2500A˚/LEdd)0.48 and L5GHz/LEdd∝(L1keV/LEdd)0.53 in the radiatively inefficient sample, respectively. Based on the similarities in radio–peak correlations, we further propose a fundamental plane in radio luminosity, the peak luminosity of blackbody radiation, and black hole mass, which is radiatively efficient: logL5GHz=1.57−0.01+0.01logLpeak−0.32−0.16+0.16logMBH−27.73−0.34+0.34 with a scatter of σR = 0.48 dex, and radiatively inefficient: logL5GHz=0.45−0.01+0.01logLpeak+0.91−0.10+0.12logMBH+12.58−0.38+0.38 with a scatter of σR = 0.63 dex. Our results are similar to those of previous studies on the fundamental plane for radiatively efficient and radiatively inefficient black hole activity. However, our results exhibit a smaller scatter, so when using the same part of blackbody radiation (i.e., the peak luminosity of the blackbody radiation), the fundamental plane becomes a little bit tighter.