The contribution of spin to jet-disk coupling in black holes

Abstract

Context. The spin of supermassive black holes could power jets from active galactic nuclei (AGN), although direct observational evidence for this conjecture is sparse. The accretion disk luminosity and jet power, on the other hand, have long been observed to follow a linear correlation. Aims. If jet power is coupled to black hole spin, deviations from the jet-disk correlation for a sample of AGN can be used to probe the dispersion of the spin parameter (a) within this sample. Methods. To obtain a large sample of radio-loud AGN, we matched double-lobed radio sources identified in Faint Images of the Radio Sky at Twenty-centimeters (FIRST, 1.4 GHz) to spectroscopically confirmed quasars from the Sloan Digital Sky Survey (SDSS). We obtain 763 FR II quasars with a median redshift of z = 1.2. Results. A tight correlation between the optical luminosity of the accretion disk and the lobe radio luminosity is observed. We estimate that 5-20% of the bolometric disk luminosity is converted to jet power. Most of the scatter to the optical-radio correlation is due to environment; deviations from jet-disk coupling due to internal factors (e.g., spin) contribute at most 0.2 dex. Conclusions. Under the assumption that the Blandford-Znajek mechanism operates in AGN, we obtain an upper limit of 0.1 dex to the dispersion of the product of the spin and the magnetic flux threading the horizon. If black hole spin determines the AGN jet efficiency, then our observations imply that all FR II quasars have very similar spin. In addition, the quasar spin distribution needs to have a wide gap to explain the radio-quiet population. The alternative, and perhaps more likely, interpretation of the tight jet-disk correlation is that black hole spin is not relevant for powering AGN jets.

Disk–Jet Connection in Active Supermassive Black Holes in the Standard Accretion Disk Regime

“…Only 2 quasars have η jet ≥ 1. This low jet production efficiency is consistent with the study by van Velzen & Falcke (2013) in which they used a correlation between optical and radio luminosities of 763 FR-II quasars utilizing the SDSS-FIRST catalog. This low efficiency is not significantly enhanced even if we set = 0.3 ( Figure 5).…”

Powers and Magnetization of Blazar Jets

“…The jet powers in FR II quasars calculated using radio-lobe calorimetry [24] are a factor ∼50 smaller than jet powers calculated using spectral fits of γ-ray detected FSRQs when assuming n p = n e jet plasma [2] (see Figure 1). Measurements of radio luminosities of extended radio-structures in some FSRQs [27,28] has enabled a comparison of the results of the two jet power measurement techniques by applying both techniques to the same objects.…”

The power and production efficiency of blazar jets

“…Problems with launching such powerful jets by standard accretion discs stimulated studies on the socalled magnetically arrested discs (MAD; Narayan et al 2003). In scenarios involving the MAD, the jet is powered by a fast spinning black hole (BH) immersed in a strong magnetic field supported by the ram pressure of the accretion flow (Tchekhovskoy et al 2011;McKinney et al 2012). As it has been theoretically estimated and numerically confirmed, the spin-extraction/MAD scenario allows launching jets with the power up to 3Ṁc 2 or so.…”

“…The applicability of the spin-extraction/MAD model to radio loud quasars was questioned by van Velzen & Falcke (2013), who, by using energetics of radio lobes, found that the median value of the jet production efficiency, η j ≡ P j /Ṁc 2 , in a radio-selected sample of quasars with double radio sources is ∼0.01. If η j depended only on the BH spin, this would imply its average value much lower than those predicted by BH cosmological evolution (Volonteri et al 2013).…”