We examine the disc–jet connection in stellar mass and supermassive black holes by investigating the properties of their compact emission in the X‐ray and radio bands. We compile a sample of ∼100 active galactic nuclei with measured masses, 5‐GHz core emission, and 2–10 keV luminosities, together with eight galactic black holes with a total of ∼50 simultaneous observations in the radio and X‐ray bands. Using this sample, we study the correlations between the radio (LR) and the X‐ray (LX) luminosity and the black hole mass (M). We find that the radio luminosity is correlated with bothM and LX, at a highly significant level. In particular, we show that the sources define a ‘Fundamental Plane’ in the three‐dimensional (log LR, log LX, log M) space, given by log LR= (0.60+0.11−0.11) log LX+ (0.78+0.11−0.09) log M+ 7.33+4.05−4.07, with a substantial scatter of σR= 0.88. We compare our results to the theoretical relations between radio flux, black hole mass, and accretion rate derived by Heinz & Sunyaev. Such relations depend only on the assumed accretion model and on the observed radio spectral index. Therefore, we are able to show that the X‐ray emission from black holes accreting at less than a few per cent of the Eddington rate is unlikely to be produced by radiatively efficient accretion, and is marginally consistent with optically thin synchrotron emission from the jet. On the other hand, models for radiatively inefficient accretion flows seem to agree well with the data.

We present a comprehensive synthesis model for the active galactic nuclei (AGN) evolution and the growth of supermassive black hole (SMBH) in the Universe. We assume that black holes accrete in just three distinct physical states, or ‘modes’: at low Eddington ratio, only a radiatively inefficient, kinetically dominated mode is allowed [low kinetic (LK)]; at high Eddington ratio, instead, AGN may display both a purely radiative [radio quiet, high radiative (HR)] and a kinetic [radio loud, high kinetic (HK)] mode. We solve the continuity equation for the black hole mass function using the locally determined one as a boundary condition, and the hard X‐ray luminosity function as tracer of the AGN growth rate distribution, supplemented with a luminosity‐dependent bolometric correction and an absorbing column distribution. Differently from most previous semi‐analytic and numerical models for black hole growth, we do not assume any specific distribution of Eddington ratios, rather we determine it empirically by coupling the mass and luminosity functions and a set of fundamental relations between observables in the three accretion modes. SMBH always show a very broad accretion rate distribution, and we discuss the profound consequences of this fact for our understanding of observed AGN fractions in galaxies, as well as for the empirical determination of SMBH mass functions with large surveys. We confirm previous results and clearly demonstrate that, at least for z≲ 1.5, SMBH mass function evolves antihierarchically, i.e. the most massive holes grew earlier and faster than less massive ones. For the first time, we find hints of a reversal of such a downsizing behaviour at redshifts above the peak of the black hole accretion rate density (z≈ 2). We also derive tight constraints on the (mass‐weighted) average radiative efficiency of AGN: under the simplifying assumption that the mass density of both high redshift (z∼ 5) and ‘wandering’ black holes ejected from galactic nuclei after merger events are negligible compared to the local mass density, we find that 0.065 < ξ0〈εrad〉 < 0.07, where ξ0 is the local SMBH mass density in units of 4.3 × 105 M⊙ Mpc−3. We trace the cosmological evolution of the kinetic luminosity function of AGN, and find that the overall efficiency of SMBH in converting accreted rest mass energy into kinetic power, εkin, ranges between εkin≃ (3–5) × 10−3, depending on the choice of the radio core luminosity function. Such a ‘kinetic efficiency’ varies however strongly with SMBH mass and redshift, being maximal for very massive holes at late times, as required for the AGN feedback by many galaxy formation models in cosmological contexts.

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We derive the non‐linear relation between the core flux Fν of accretion‐powered jets at a given frequency and the mass M of the central compact object. For scale‐invariant jet models, the mathematical structure of the equations describing the synchrotron emission from jets enables us to cancel out the model‐dependent complications of jet dynamics, retaining only a simple, model‐independent algebraic relation between Fν and M. This approach allows us to derive the Fν–M relation for any accretion disc scenario that provides a set of input boundary conditions for the magnetic field and the relativistic particle pressure in the jet, such as standard and advection‐dominated accretion flow (ADAF) disc solutions. Surprisingly, the mass dependence of Fν is very similar in different accretion scenarios. For typical flat‐spectrum core‐dominated radio jets and standard accretion scenarios, we find Fν∼M17/12. The 7–9 orders of magnitude difference in black hole mass between microquasars and active galactic nuclei (AGN) jets imply that AGN jets must be about 3–4 orders of magnitude more radio‐loud than microquasars, i.e. the ratio of radio to bolometric luminosity is much smaller in microquasars than in AGN jets. Because of the generality of these results, measurements of this Fν–M dependence are a powerful probe of jet and accretion physics. We show how our analysis can be extended to derive a similar scaling relation between the accretion rate and Fν for different accretion disc models. For radiatively inefficient accretion modes, we find that the flat‐spectrum emission follows .

We present the first results from a 500 ks Chandra ACIS-I observation of M87. At soft energies (0.5Y1.0 keV), we detect filamentary structures associated with the eastern and southwestern X-ray and radio arms. Many filaments are spatially resolved with widths of $300 pc. This filamentary structure is particularly striking in the eastern arm, where we suggest the filaments are outer edges of a series of plasma-filled, buoyant bubbles whose ages differ by $6 ; 10 6 yr. These X-ray structures may be influenced by magnetic filamentation. At hard energies (3.5Y7.5 keV), we detect a nearly circular ring of outer radius 2.8 0 (13 kpc), which provides an unambiguous signature of a weak shock, driven by an outburst from the supermassive black hole (SMBH ). The density rise in the shock is shock / 0 % 1:3 (Mach number, M % 1:2). The observed spectral hardening in the ring corresponds to a temperature rise T shock /T 0 % 1:2, or M % 1:2, in agreement with the Mach number derived independently from the gas density. Thus, for the first time, we detect gas temperature and density jumps associated with a classical shock in the atmosphere around a SMBH. We also detect two additional surface brightness edges and pressure enhancements at radii of $0.6 0 and $1 0 . The $0.6 0 feature may be overpressurized thermal gas surrounding the relativistic plasma in the radio cocoon, the ''piston,'' produced by the current episode of AGN activity. The overpressurized gas is surrounded by a cool gas shell. The $1 0 feature may be an additional weak shock from a secondary outburst. In an earlier episode, the piston was responsible for driving the 2.8 0 shock.