Transcript Solitons in Large Scale Multi-Component Systems - INFN-LNF

Electromagnetic and Radiative
Processes Near Black Hole Event
Horizon
Kinwah Wu (MSSL, University College London)
Steven Von Fuerst (KIPAC, Stanford University)
Warrick Ball (P&A, University College London)
Living with black holes
- artists’ impression
(images from http://www.musemessenger.com)
Black holes are very simple objects
What do black hole have?
- a singularity
- an event horizon
Schwarzschild radius
Do black hole exist?
Who knows …… but ……
Astrophysical zoo of “black holes” ………
1. Stellar mass black holes
- dead corpses of very massive stars
2. Supermassive black holes
- monsters at the centres of galaxies
3. Intermediate mass black holes (?)
- “the new kids on the block”
ultra-luminous X-ray sources (ULX)
4. Primordial black holes
- fossils of the distant past
a ULX in the starburst galaxy M82
(image from science@nasa)
What we have seen .… what we are
believing ….
Artists’ production based on
astrophysicists’ interpretation
Observational images
(image from http://chandra.harvard.edu/photo/2004/rxj1242)
X-ray lines from accretion disks
around black holes
Time-averaged line profiles of
Fe K alpha emission from the
AGN MCG-6-30-15 obtained
by the ASCA satellite.
from Fabian et al. (2000)
Relativistic energy shift in ray tracing:
“Usual” line emission calculations
The standard recipe:
- define the metric and calculate the geodesic
- make a Keplerian thin disk (i.e. velocity profile of the emitters)
- determine the energy shift relative to the observed at each disk pixel
- sum the contribution of emission from each pixel
But, …. how about radiative transfer effects? … Absorption? Scattering?
Also, ….. what if the disk is not geometrically thin or Keplerian? …
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Formulating general relativistic
radiative transfer
Liouville’s
Theorem
Boltzmann
Equation
BBGKY
Hierarchy
Radiative Transfer
Equation in a
Covariant Form
General
Relativity
- phase-space volume conservation
- particle number conservation in the comoving frame
no scattering
(Fuerst & Wu 2004, 2007; Wu et al. 2006)
Resonant scattreing in the relativistic
frame work
Juetter distribution
constraints (conservation and covariant resonant conditions):
Fuerst & Wu (2004)
General relativistic radiative transfer
- absorption and emission
Profiles of absorption and emission lines from thin accretion disks around
Schwarzschild and Kerr black holes with a = 0.998, viewed at inclinations
of 45o and 85o (top and bottom rows respectively). (Fuerst & Wu 2004)
General relativistic radiative transfer
- angle dependent emission
Accretion-disk images showing the
pitch angles of photons (in the
local emitters’ frame) that can
reach a distant observer. The disk
images are viewed at inclination
angles of 45o (left panels) and 85o
(right panels). Disks around a
Schwarzschild black hole are on
the top row, and disks around a
Kerr black hole (a = 0.998) are on
the bottom row.
Wu et al. (2006)
Emission from 3D objects around a
black hole
i = 45o
i = 85o
energy-shift torus image
Profiles of emission lines from opaque relativistic
accretion tori with an aspect ratio set by a
velocity law, with index n = 0.232 and rk = 8rg as
indicated in MRI accretion disk simulations
Fuerst and Wu (2007)
Emission optically thick accretion tori
Energy-shift images of tori
(n = 0.2) around Kerr black
holes (a = 0.998), with a
large aspect ratio such that
the inner boundary of the
emission surface reaches
the black-hole event
horizon. Viewing inclination
angle i = 15o, 45o and 85o
(panels in top row, from left
to right).
Fuerst and Wu (2007)
Emission from semi-opaque accretion
tori
Lines with different energies can resonate in semi-transparent tori
Wu et al. (2008)
Time-dependent calculations
Synchrotron and free-free emission from accretion inflows and outflows in
the vicinity of a Kerr black hole (obtained by GRMHD simulations).
Fuerst et al. (2007)
General relativistic radiative transfer
in the presence of scattering
General relativistic transfer in the presence of scattering
- a global integral equation instead of a local differential equation
tensor moment function
the radiative transfer equation in stationary space-time
first-order tensor
moment equation
+ higher-order moment equations …
the energy “Doppler” shift factor
Fuerst (2005), Wu et al. (2008)
Scattering dominated accretion tori
around a black hole
(Fuerst 2005, PhD Thesis)
Seeing is believing
imaging black hole and shadowing
Shadows of background sky cast by a Schwarzschild black hole
with spherical (left) and gaussian (right) planar matter distributions
Ball and Wu (2008)
Can all black holes be imaged by
shadowing?
black hole
incident electro-magnetic plane waves
There are always some big photons which cannot be fit inside a
black hole!
Black holes as particle scatterer
At infinity
Near the event horizon
Klein-Gordon plane waves
Black hole scattering
- Plane wave-like behaviour at infinity and near the black hole
event horizon
Potential scattering:
One can define the emission and absorption coefficient of black hole.
(cf radiative processes of atomic matter)
Black holes are not black after all …
They are actually gray holes in disguise.
Event horizon revisited
- boundary of no return
- surface of infinite red-shift
- surface at which waves piled up
……
Making black hole event horizon in the
laboratory
an artificial event horizon (photon
trapped surface) is developed at
the leading edge of the first laser
pulse
laser
optical fibre
The first laser pulse to modify the
property of the optical fibre
The second pulse, at a different wavelength, as
the probing wave
Leohardt et al. (2007)
Electrodynamics near black hole
event horizon
My own questions:
How do information transfer near the event horizon?
Can we have a classical treatment?
What is the role of gravity?
My thought experiment:
Suppose that we thread the optical fibre with a magnetic field,
do the magnetic field on the left side and the right side of the
laser induced event horizon communicate (classically)?
laser
optical fibre
What do we know about the black hole
event horizon?
What do we know about black holes?
?
?
?
I want to believe ……
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