ALBERT

Description: It is very controversial whether radio–X-ray correlation as defined in low-hard state of X-ray binaries (XRBs) can extend to quiescent state (e.g. X-ray luminosity less than a critical value of L X,c  ~ 10 –5.5 L Edd ) or not. In this work, we collect a sample of XRBs and low-luminosity active galactic nuclei (LLAGNs) with wide distribution of Eddington ratios ( L X / L Edd  ~ 10 –9 –10 –3 ) to re-explore the Fundamental Plane between 5 GHz radio luminosity, L R , 2–10 keV X-ray luminosity, L X , and black hole (BH) mass, M BH , namely log L R = X log L X + M log M BH + constant. For the whole sample, we confirm the former Fundamental Plane of Merloni et al. and Falcke et al. that X  ~ 0.6 and M  ~ 0.8 even after including more quiescent BHs. The quiescent BHs follow the Fundamental Plane very well, and, however, FR I radio galaxies follow a steeper track comparing other BH sources. After excluding FR Is, we investigate the Fundamental Plane for BHs in quiescent state with L X  〈  L X,c and sub-Eddington BHs with L X  〉  L X,c , respectively, and both sub-samples have a similar slope, X  ~ 0.6, which support that quiescent BHs may behave similar to those in low-hard state. We further select two sub-samples of AGNs with BH mass in a narrow range (FR Is with M BH  = 10 8.8±0.4 and other LLAGNs with M BH  = 10 8.0±0.4 ) to simulate the behaviour of a single supermassive BH evolving from sub-Eddington to quiescent state. We find that the highly sub-Eddington sources with L X / L Edd  ~ 10 –6 –10 –9 still roughly stay on the extension of radio–X-ray correlation as defined by other sub-Eddington BHs. Our results are consistent with several recent observations in XRBs that the radio–X-ray correlation as defined in low-hard state can extend to highly sub-Eddington quiescent state.

Description: It is very controversial whether radio–X-ray correlation as defined in low-hard state of X-ray binaries (XRBs) can extend to quiescent state (e.g. X-ray luminosity less than a critical value of L X,c  ~ 10 –5.5 L Edd ) or not. In this work, we collect a sample of XRBs and low-luminosity active galactic nuclei (LLAGNs) with wide distribution of Eddington ratios ( L X / L Edd  ~ 10 –9 –10 –3 ) to re-explore the Fundamental Plane between 5 GHz radio luminosity, L R , 2–10 keV X-ray luminosity, L X , and black hole (BH) mass, M BH , namely log L R = X log L X + M log M BH + constant. For the whole sample, we confirm the former Fundamental Plane of Merloni et al. and Falcke et al. that X  ~ 0.6 and M  ~ 0.8 even after including more quiescent BHs. The quiescent BHs follow the Fundamental Plane very well, and, however, FR I radio galaxies follow a steeper track comparing other BH sources. After excluding FR Is, we investigate the Fundamental Plane for BHs in quiescent state with L X  〈  L X,c and sub-Eddington BHs with L X  〉  L X,c , respectively, and both sub-samples have a similar slope, X  ~ 0.6, which support that quiescent BHs may behave similar to those in low-hard state. We further select two sub-samples of AGNs with BH mass in a narrow range (FR Is with M BH  = 10 8.8±0.4 and other LLAGNs with M BH  = 10 8.0±0.4 ) to simulate the behaviour of a single supermassive BH evolving from sub-Eddington to quiescent state. We find that the highly sub-Eddington sources with L X / L Edd  ~ 10 –6 –10 –9 still roughly stay on the extension of radio–X-ray correlation as defined by other sub-Eddington BHs. Our results are consistent with several recent observations in XRBs that the radio–X-ray correlation as defined in low-hard state can extend to highly sub-Eddington quiescent state.

Description: Because the disc–jet coupling likely depends on various properties of sources probed, the sample control is always an important but challenging task. In this work, we re-analyzed the INTEGRAL hard X-ray-selected sample of Seyfert galaxies. We only consider sources that have measurements in black hole mass, and luminosities in radio and X-rays. Our final sample includes 64 (out of the original 79) sources, consists of both bright AGNs and low-luminosity ones. The 2-10 keV X-ray Eddington ratio LX/LEdd locates in the range between ∼10−4.5 and ∼10−0.5. We first find that, because of the similarity in the LHX/LX distribution, the X-ray origin of radio-loud Seyferts may be the same to that of radio-quiet ones, where we attribute to the hot accretion flow (or similarly, the corona). We then investigate the connections between luminosities in radio and X-rays. Since our sample suffers a selection bias of a black hole mass MBH dependence on LX/LEdd, we focus on the correlation slope ξX between the radio (at 1.4 GHz) and X-ray luminosities in Eddington unit, i.e. $({L_{ m R}}/{L_{ m Edd}}) propto ({L_{ m X}}/{L_{ m Edd}})^{xi _{ m X}}$. We classify the sources according to various properties, i.e. 1) Seyfert classification, 2) radio loudness, and 3) radio morphology. We find that, despite these differences in classification, all the sources in our sample are consistent with a universal correlation slope ξX (note that the normalization may be different), with ξX = 0.77 ± 0.10. This is unexpected, considering various possible radio emitters in radio-quiet systems. For the jet (either relativistic and well collimated, or sub-relativistic and weakly collimated) interpretation, our result may suggest a common/universal but to be identified jet launching mechanism among all the Seyfert galaxies, while properties like black hole spin and magnetic field strength only play secondary roles. We further estimate the jet production efficiency ηjet of Seyfert galaxies, which is $eta _{ m jet}approx 1.9^{+0.9}_{-1.5}imes 10^{-4}$ on average. We also find that ηjet increases as the system goes fainter. Alternative scenarios for the radio emission in radio-quiet systems are also discussed.