535 research outputs found
The jet-disc connection: evidence for a reinterpretation in radio loud and radio quiet active galactic nuclei
To constrain models of the jet-disc connection, we explore Eddington ratios
reported in Foschini (2011) and interpret them in relation to the values in
Sikora et al. across the active galactic nuclei population from radio loud
quasars, their flat spectrum radio quasar subclass, the recently discovered
gamma-ray loud narrow-line type 1 Seyfert galaxies, Fanaroff-Riley type I (FRI)
radio galaxies and radio quiet quasars of the Palomar Green survey. While
appeal to disc truncation in radiatively inefficient flow appears to explain
the observed inverse relation between radio loudness and Eddington ratio in
radio loud and radio quiet quasars, FR I objects, scale invariance and recent
data on powerful jets in narrow-line Seyfert 1 galaxies offer compelling
arguments in favour of a reinterpretaion of the jet-disc connection
Constraints on the radio loud/radio quiet dichotomy from the fundamental plane
The fundamental plane for black hole activity constitutes a tight correlation
between jet power, X-ray luminosity, and black hole mass. Under the assumption
that a Blandford-Znajek-type mechanism, which relies on black hole spin,
contributes non-negligibly to jet production, the sufficiently small scatter in
the fundamental plane shows that black hole spin differences of
a1 are not typical among the active galactic nuclei
population. If as it seems radio loud and radio quiet objects are both
faithful to the fundamental plane, models of black hole accretion in which the
radio loud/radio quiet dichotomy is based on a spin dichotomy of
a1/a0, respectively, are difficult to reconcile with the
observations.
We show how recent theoretical work based on differences in accretion flow
orientation between retrograde and prograde, accommodates a small scatter in
the fundamental plane for objects that do have non-negligible differences in
black hole spin values. We also show that the dichotomy in spin between the
most radio loud and the most radio quiet involves a0. And, finally, we show how the picture that produces compatibility
with the fundamental plane, also allows one to interpret other otherwise
puzzling observations of jets across the mass scale including 1) the recently
observed inverse relation between radio and X-rays at higher Eddington ratios
in both black hole X-ray binaries as well as active galactic nuclei and 2) the
apparent contradiction between jet power and black hole spin observed in X-ray
hard and transitory burst states in X-ray binaries.Comment: 8 pages, 1 figure, accepted in MNRA
The Jet-disk Connection: Evidence for a Reinterpretation in Radio-loud and Radio-quiet Active Galactic Nuclei
To constrain models of the jet-disc connection, we explore Eddington ratios reported in Foschini (2011) and interpret them in relation to the values in Sikora et al. across the active galactic nuclei population from radio loud quasars, their flat spectrum radio quasar subclass, the recently discovered gamma-ray loud narrow-line type 1 Seyfert galaxies, Fanaroff-Riley type I (FRI) radio galaxies and radio quiet quasars of the Palomar Green survey. While appeal to disc truncation in radiatively inefficient flow appears to explain the observed inverse relation between radio loudness and Eddington ratio in radio loud and radio quiet quasars, FR I objects, scale invariance and recent data on powerful jets in narrow-line Seyfert 1 galaxies offer compelling arguments in favour of a reinterpretaion of the jet-disc connection
Magnetic Fields Threading Black Holes: Restrictions from General Relativity and Implications for Astrophysical Black Holes
The idea that black hole spin is instrumental in the generation of powerful jets in active galactic nuclei and X-ray binaries is arguably the most contentious claim in black hole astrophysics. Because jets are thought to originate in the context of electromagnetism, and the modeling of Maxwell fields in curved spacetime around black holes is challenging, various approximations are made in numerical simulations that fall under the guise of ‘ideal magnetohydrodynamics’. But the simplifications of this framework may struggle to capture relevant details of real astrophysical environments near black holes. In this work, we highlight tension between analytic and numerical results, specifically between the analytically derived conserved Noether currents for rotating black hole spacetimes and the results of general relativistic numerical simulations (GRMHD). While we cannot definitively attribute the issue to any specific approximation used in the numerical schemes, there seem to be natural candidates, which we explore. GRMHD notwithstanding, if electromagnetic fields around rotating black holes are brought to the hole by accretion, we show from first principles that prograde accreting disks likely experience weaker large-scale black hole-threading fields, implying weaker jets than in retrograde configurations
Counter-rotating black holes from FRII lifetimes
Estimates suggest that while FRII jets appear to have lifetimes constrained
to hundreds of millions of years, radio galaxies with FRI jets appear to be
longer lived. We illustrate the nature of this time constraint from model
perspectives, showing how compatibility between theory and data match in a way
suggesting a key difference between active galaxies whose engines are
characterized by accretion onto co-rotating versus counter-rotating black
holes. We calculate a range of timescales for counter-rotating black holes for
a range of accretion rates compatible with theory which we then compare to
data. The validity of these timescales constitutes the most powerful recent
piece of evidence for considering counter-rotation between black holes and
accretion disks in high energy astrophysics
FR0 Radio Galaxies and Their Place in the Radio Morphology Classification
So-called FR0 radio galaxies have recently emerged as a family of active galaxies with all the same properties as FRI radio galaxies except for their ratio of core to total emission, which is about 30 times higher than that of FRI sources. We show how their properties fit within the gap paradigm as low, prograde, spinning black holes whose progenitors are powerful FRII quasars that transitioned rapidly from the cold mode into advection-dominated accretion over a few million years. The prediction is that if sufficient fuel exists, FR0 radio galaxies will evolve into full-fledged FRI radio galaxies and the observational dearth of FRI radio galaxies compared to FR0s at low redshift tells us about the supply of gas in the low-redshift FR0s. Given the model prescription, this 5–1 FR0 to FRI ratio implies that at low redshift, the FRII quasar class of active galaxies struggles to fuel its black hole beyond 1.3 times its original mass. In addition to this, we illustrate model prescriptions for the black hole mass, black hole spin, redshift, and environment distribution for FR0 radio galaxies by fitting them within a paradigm that views them as a continuous class of active galaxies that are sandwiched between FRII quasars and FRI radio galaxies
The emergence of the X-ray luminosity/cluster richness relation for radio galaxies
The idea that mergers are more likely in dense groups or clusters coupled
with the assumption that such events lead to cold gas flows onto black holes,
suggests a direct relationship between the radiative efficiency of an active
galactic nucleus and environmental richness. Observations, however,
increasingly challenge this and other basic expectations. Mounting evidence,
for example, shows an inverse trend between near-Eddington accreting objects
and environmental richness. Broken down by radio galaxy subgroup, recent work
has explored connections between low excitation radio galaxies with
Fanaroff-Riley II jet morphology (FRII LERGs) and other radio galaxies. We make
contact with that work by adding a discussion of the recently discovered FR0
radio galaxies and show how to fit them in a picture in which FRII LERGs are
not initial nor final phases in the lifetime of a radio galaxy, but de facto
transition states. We describe how to understand the observed X-ray
luminosity/cluster richness relation as a fundamental correlation on the nature
of the jet-disk connection
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