BLACK HOLE SPIN AND THE RADIO LOUD/QUIET DICHOTOMY OF ACTIVE GALACTIC NUCLEI

By A. Tchekhovskoy, Ramesh Narayan, J. McKinney. 2009

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Radio loud active galactic nuclei (AGNs) are on average 1000 times brighter in the radio band compared to radio quiet AGNs. We investigate whether this radio loud/quiet dichotomy can be due to differences in the spin of the central black holes (BHs) that power the radio-emitting jets. Using general relativistic magnetohydrodynamic simulations, we construct steady state axisymmetric numerical models for a wide range of BH spins (dimensionless spin parameter 0.1 ⩽ a ⩽ 0.9999) and a variety of jet geometries. We assume that the total magnetic flux through the BH horizon at radius rH(a) is held constant. If the BH is surrounded by a thin accretion disk, we find that the total BH power output depends approximately quadratically on the angular frequency of the hole, P ∝ Ω2H ∝ (a/rH)2. We conclude that, in this scenario, differences in the BH spin can produce power variations of only a few tens at most. However, if the disk is thick such that the jet subtends a narrow solid angle around the polar axis, then the power dependence becomes much steeper, P ∝ Ω4H or even ∝Ω6H. Power variations of 1000 are then possible for realistic BH spin distributions. We derive an analytic solution that accurately reproduces the steeper scaling of jet power with ΩH and we provide a numerical fitting formula that reproduces all our simulation results. We discuss other physical effects that might contribute to the observed radio loud/quiet dichotomy of AGNs.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/3a0f109d20d0ff75dff1dce870de3829ebba1a3f

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Citations in the corpus

General relativistic magnetohydrodynamic simulations of magnetically choked accretion flows around black holes (2012, background): “…flux comes from large radii, as implicit in outflow models (Blandford 1976; Blandford & Znajek 1977; Blandford & Payne 1982; Narayan et al. 2007; Tchekhovskoy et al. 2009, 2010a,b), but transport of flux from large radii may be inefficient (Lubow et al. 1994; Spruit & Uzdensky 2005; Rothstein &…”
Prograde and retrograde black holes: whose jet is more powerful? (2012, neutral): “…spin, ΩH = ac/2rH is BH angular frequency, f (ΩH) ≈ 1 + 1.38(ΩHrg/c)2 − 9.2(ΩHrg/c)4 is a high-spin correction, dAθϕ = √−g dθdϕ is an area element in θ−ϕ plane, and g is the metric determinant (Tchekhovskoy et al. 2010, see also BZ; Lee et al. 2000; Komissarov 2001; Tanabe & Nagataki 2008).”
EVIDENCE FOR LOW BLACK HOLE SPIN AND PHYSICALLY MOTIVATED ACCRETION MODELS FROM MILLIMETER-VLBI OBSERVATIONS OF SAGITTARIUS A* (2010, background): “…magnetohydrodynamic and radiative-hydrodynamic simulations playing a central role (De Villiers et al. 2005; McKinney 2006; Hawley & Krolik 2006; Beckwith et al. 2008; McKinney & Blandford 2009; Tchekhovskoy et al. 2010; Dexter et al. 2010; Penna et al. 2010; Kurosawa & Proga 2009).”
Black Hole Spin via Continuum Fitting and the Role of Spin in Powering Transient Jets (2013, background): “…eﬀect predicts that the jet eﬃciency factor should vary as η jet ∝ a 2 ∗ (Ruﬃni & Wilson 1975; Blandford & Znajek 1977) or, more precisely, as η jet ∝ Ω 2H (Tchekhovskoy et al. 2010), where Ω H is the angular frequency of the black hole horizon 10 , The dashed line in Figure 6a corresponds…”
FEEDBACK IN LUMINOUS OBSCURED QUASARS (2011, background): “…this mechanism as the primary mode of BH feedback would require all galaxies to have undergone a radio-loud phase – a conjecture which lacks direct evidence and contradicts atheoretical paradigm in which radio-loudness is determined bythe spin of the black hole (e.g., Tchekhovskoy et al. 2010).”
A Reconnection Switch to Trigger gamma-Ray Burst Jet Dissipation (2010, methodology): “…generalized axisymmetric steady-state jet solution is presented as based upon approximate analytical solutions that have been confirmed numerically (Tchekhovskoy et al. 2008, 2009, 2010b) using the HARM code (Gammie, McKinney & Tóth 2003; Noble et al. 2006; Mignone & McKinney 2007; Tchekhovskoy,…”
Grand unification of AGN activity in the ΛCDM cosmology (2009, background): “By including higher order corrections it can be shown that the dependance ofLjet on a can be much steeper for rapidly rotating BHs (Ljet ∼ a4; Tanabe & Nagataki 2008; see also Tchekhovskoy et al. 2010 for a recent study of the dynamic l range ofLjet predicted by these solutions).”
Efficient Generation of Jets from Magnetically Arrested Accretion on a Rapidly Spinning Black Hole (2011, background): “Tchekhovskoy et al. (2010) showed that the modified form written here, with f ( H) = 1, is accurate even for large spins up to a ≈ 0.95, while for yet larger spins, they gave a more accurate sixth order approximation, f ( H) ≈ 1 + 1.38( Hrg/c)2 − 9.2( Hrg/c)4.”
Relativistic MHD simulations of core-collapse GRB jets: 3D instabilities and magnetic dissipation (2015, background): “It is also conceivable that if the plasma undergoes a rapid expansion phase when exiting the star, parts of it may attain a low enough magnetisation (Tchekhovskoy et al. 2010b), and the internal shocks may become effective; however, it is unclear if these parts carry sufficient amounts of energy to…”
Hot Accretion Flows Around Black Holes (2014, methodology): “At its most basic, the outflowing power in the BZ model is given by (Blandford & Znajek 1977; see Tchekhovskoy et al. 2010 for more accurate approximations) PBZ = κ 4πc Φ2Ω2H, (30) where Φ is the magnetic flux threading the horizon, ΩH = a∗c/2RH is the angular velocity of the horizon, a∗ ≡ a/M is…”
Measuring the spins of accreting black holes (2011, background): “If relativistic jets are powered by black hole spin, then theory predicts that jet power will increase dramatically with increasing a∗ (Tchekhovskoy et al 2010).”
Observational evidence for a correlation between jet power and black hole spin (2011, background): “Tchekhovskoy et al. (2010) obtained a more accurate theoretical scaling which works up to spins fairly close to unity: Pjet ∝ 2H, where H is the angular frequency of the BH horizon, H = a∗(c3/2GM)/(1 + √ 1 − a2∗).”
Observations of feedback from radio-quiet quasars - I. Extents and morphologies of ionized gas nebulae (2013, background): “…mechanism as the primary mode of limiting galaxy mass would require all galaxies to have undergone a radio-loud phase – a conjecture which lacks direct evidence and contradicts a theoretical paradigm in which radio-loudness is determined by the spin of the black hole (Tchekhovskoy et al. 2010).”