Radio Loudness of Active Galactic Nuclei: Observational Facts and Theoretical Implications

By M. Sikora, Ł. Stawarz, Jan Lasota. 2006

405 citations recorded by the source corpus.

We investigate how the total radio luminosity of AGN-powered radio sources depends on their accretion luminosity and the central black hole mass. Our studies cover about 7 orders of magnitude in accretion luminosity (expressed in Eddington units, i.e., as Eddington ratios) and the full range of AGN black hole masses. We find that AGNs form two distinct and well-separated sequences on the radio-loudness-Eddington-ratio plane. The "upper" sequence is formed by radio-selected AGNs, and the "lower" sequence contains mainly optically selected objects. Whereas an apparent "gap" between the two sequences may be an artifact of selection effects, the sequences themselves mark the real upper bounds of radio loudness of two distinct populations of AGNs: those hosted respectively by elliptical and disk galaxies. Both sequences show the same dependence of the radio loudness on the Eddington ratio (an increase with decreasing Eddington ratio), which suggests that the normalization of this dependence is determined by the black hole spin. This implies that central black holes in giant elliptical galaxies have (on average) much larger spins than black holes in spiral/disk galaxies. This galaxy-morphology-related radio dichotomy breaks down at high accretion rates where the dominant fraction of luminous quasars hosted by elliptical galaxies is radio quiet. This led to speculations in the literature that formation of powerful jets at high accretion rates is intermittent and related to switches between two disk accretion modes, as directly observed in some black hole X-ray binaries. We argue that such intermittency can be reconciled with the spin paradigm, provided that successful formation of relativistic jets by rotating black holes requires collimation by MHD outflows from accretion disks.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/529d0ab39973d4a847e8ca94ea9f3eeb6eb2a40c

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Citations in the corpus

Mechanical feedback from active galactic nuclei in galaxies, groups and clusters (2012, background): “A connection between a black hole’s rotation rate and its energetic output has been inferred from an apparent dichotomy between rapidly-spinning, radio loud AGN and slowly spinning, radio quiet AGN (Sikora et al 2007, Martı́nez-Sansigre and Rawlings 2011, Wu et al 2011).”
THE FUNDAMENTAL PLANE OF ACCRETION ONTO BLACK HOLES WITH DYNAMICAL MASSES (2009, background): “When we only use the 8 LINER and unclassified LLAGN sources, our fit becomes µ0 = 0.70±0.11 cr = 0.48±0.14 cx =−0.07±0.12, (7) with a scatter ofσ0 = 0.25, substantially smaller than other intrinsic scatter measurements found for this relation andctually smaller than the scatter in theM–σ andM–”
Radio transients from stellar tidal disruption by massive black holes (2011, background): “Furthermore, the ‘radio loudness dichotomy’ (e.g. Ho 2002; Sikora et al. 2007) suggests that a ‘second parameter’ other thanṀ, such as the black hole spin (Wilson & Colbert 1995) or the magnetic flux threading the disk (Spruit & Uzdensky 2005), may also control the jet power.”
THE EVOLUTION OF SWIFT/BAT BLAZARS AND THE ORIGIN OF THE MeV BACKGROUND (2009, background): “Sikora et al. (2007) found out that on a radio-loudness/Eddington-ratio diagram elliptical and disk/spiral galaxies form different sequences and invoke the spin as the black hole parameter which might explain this different behavior.”
THE SPIN OF THE SUPERMASSIVE BLACK HOLE IN NGC 3783 (2011, background): “…the spin of the central supermassive black hole (SMBH) is a crucial parameter in determining whether an AGN can form powerful jets (i.e., whether the source is radio-quiet or radio-loud; Wilson & Colbert 1995), although the accretion rate/mode must clearly have a role to play (Sikora et al. 2007).”
Grand unification of AGN activity in the ΛCDM cosmology (2009, methodology): “The observational data suffer from multiple selection effects, which may be responsible for the apparent dichotomy seen in the distribution (see discussion by Sikora et al. 2007).”
Selection bias in dynamically measured supermassive black hole samples: its consequences and the quest for the most fundamental relation (2016, result): “…would imply that most of the local black holes are spinning rapidly, suggesting that spin may not be the only parameter controlling radio loudness in AGN, in line with many other, independent lines of evidenc (e.g., Sikora et al. 2007; Shankar et al. 2008, 2010b, 2016, and references therein).”
No evidence for black hole spin powering of jets in X-ray binaries (2010, background): “The strongest case made in recent years for spin-powering ofsome AGN jets is that put forward by Sikora et al. (2007), who demonstrate an apparent bimodality in the relation of radio loudness as a function of Eddington ratio for different classes of AGN (see also e.g. Lal & Ho 2009).”
Neutral hydrogen in galaxy haloes at the peak of the cosmic star formation history (2014, background): “It is noteworthy that radio-quiet quasars are more common than radio-loud quasars by a factor ∼ 10 (e.g., Sikora et al. 2007).”
BLACK HOLE SPIN AND THE RADIO LOUD/QUIET DICHOTOMY OF ACTIVE GALACTIC NUCLEI (2009, methodology): “In the context of the radio loud/quiet dichotomy of AGNs, following Sikora et al. (2007) let us assume that supermassive BHs in elliptical galaxies, which manifest themselves as radio loud AGNs, have higher spin parameters with a median a ∼ 0.9, while the BHs in spirals, the radio quiet AGNs, have…”