Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.atnf.csiro.au/research/cena/documents/presentations/bicknell.pdf Дата изменения: Thu Jul 16 04:36:52 2009 Дата индексирования: Fri Nov 27 09:05:42 2009 Кодировка: Поисковые слова: m 43

Movies available at: http://www.mso.anu.edu.au/~geoff/CentaurusA and http://www.mso.anu.edu.au/~geoff/PGN09

Centaurus A: Some Core Physics
Credit: Helmut Steinle http://www.mpe.mpg.de/~hcs/Cen-A/

Geoff Bicknell1 Jackie Cooper1 Cuttis Saxton1 Ralph Sutherland1 Stefan Wagner2 1. Research School of Astronomy Astrophysics, ANU 2. Landessternwarte, University of Heidelberg


This talk

· Transition to turbulence · TeV emission · Jet-cloud interactions in core

Many Faces of Centaurus A Sydney July 2009

2


Transition to turbulence
Transonic flow

Flaring region: supersonic -> transonic transition

Relativistic supersonic jet

Credit: Hardcastle et al. 2003

Many Faces of Centaurus A Sydney July 2009

3


Decelerating relativistic jets (GB ApJ `95)
c2 R= 4p

Perturbation V

Critical Mach Number Mc = 1 + sec2 -
2

Many Faces of Centaurus A Sydney July 2009

4


Expect transition to turbulent flow around ~ 0.6 ­ 0.8 Laing and colleagues: Analysis of brightness asymmetries of 8 FR1 jets ­ Transition occurs around 0.8 c

Many Faces of Centaurus A Sydney July 2009

5


From GB, ApJ, 1984

·Transition to fully turbulent

flow involves immersed shocks

· Symmetric shocks perturbed
by m=1 KH instability

Many Faces of Centaurus A Sydney July 2009

6


TeV emission: Example PKS 2155-304

Credits: Piner, Plant & Edwards

Credits: HESS consortium

Many Faces of Centaurus A Sydney July 2009

7


Example of fitting spectrum

ATOM

RXTE Swift

HESS

Many Faces of Centaurus A Sydney July 2009

8


Example of fitting spectrum
1 b 2

= = =

2.0 eV 2.5 в 103 eV 3.0 в 10
4

ATOM

RXTE Swift

HESS

Many Faces of Centaurus A Sydney July 2009

8


Example of fitting spectrum
1 b 2

= = =

2.0 eV 2.5 в 103 eV 3.0 в 10
4

1 b 2

= 8.5 в 10 = 3.0 в 10 = 1.4 в 10

3 5 6

ATOM

RXTE Swift

HESS

Many Faces of Centaurus A Sydney July 2009

8


Example of fitting spectrum
1 b 2

= = =

2.0 eV 2.5 в 10 eV
3

3.0 в 10

4

3e = B 2 me c

1
2

b 2

= 8.5 в 10 = 3.0 в 10 = 1.4 в 10

3 5 6

ATOM

RXTE Swift

HESS

Many Faces of Centaurus A Sydney July 2009

8


Example of fitting spectrum
1 b 2

= = =

2.0 eV 2.5 в 10 eV
3

3.0 в 10

4

3e = B 2 me c B R = 0.040 G = 3.3 в 10 = 40

1
2

b 2 cm
-3

= 8.5 в 10 = 3.0 в 10 = 1.4 в 10

3 5 6

ATOM

16

K

RXTE Swift



= 6.5 в 107 cm

HESS

Many Faces of Centaurus A Sydney July 2009

8


Shock spectrum
If electrons accelerated at shock and cool in constant magnetic field in a region of size L then volume averaged shock spectrum given by:
Ї N ( ) = = where b = K b a-1 K b a-1 vsh AL a-1 1 - (1 - ) b > b

-(a+1) -(a+1)

< b

Many Faces of Centaurus A Sydney July 2009

9


Soft photon spectrum
· Klein-Nishina effects limit soft photons to low energy and
scattering electrons to high energy
<
2

0

(me c2 )2
2 -1 -1

0.26 >

TeV

me c2

2.0 в 106

TeV

· Soft photon input: 0.1 x Blackbody with mean temperature ~
200 K
Many Faces of Centaurus A Sydney July 2009 10


AX1C ­ possible site of TeV emission
Hard X-ray synchrotron spectrum indicates reasonable population of high energy electrons

Many Faces of Centaurus A Sydney July 2009

11


Centaurus A
Unusual spectrum ­ extending from peak at ~ 100 keV to beyond a TEV

External Inverse Compton "fit"

Many Faces of Centaurus A Sydney July 2009

12


Parameters
a=
b

2 0.8 22 1.0 в 10 2 в 10
8 5

= = = = = =

0.2 eV

= 60 = 1.44


1 b 2 B T
dust dust

Energy density = 1.3 в 10 = 200 K = 0.1

8.0 в 10

-4

-10

= 2 в Equipartition ergs cm
-3

Many Faces of Centaurus A Sydney July 2009

13


PPMLR simulation code

Many Faces of Centaurus A Sydney July 2009

13 14


PPMLR simulation code
Based upon Godunov method of numerical hydrodynamics

Many Faces of Centaurus A Sydney July 2009

13 14


PPMLR simulation code
Based upon Godunov method of numerical hydrodynamics Piecewise Parabolic Method with Lagrangian remap (PPMLR) and Riemann solver

Many Faces of Centaurus A Sydney July 2009

13 14


PPMLR simulation code
Based upon Godunov method of numerical hydrodynamics Piecewise Parabolic Method with Lagrangian remap (PPMLR) and Riemann solver Originated from VH1 code (University of Virginia and University of Nth Carolina)

Many Faces of Centaurus A Sydney July 2009

13 14


PPMLR simulation code
Based upon Godunov method of numerical hydrodynamics Piecewise Parabolic Method with Lagrangian remap (PPMLR) and Riemann solver Originated from VH1 code (University of Virginia and University of Nth Carolina) Added cooling of thermal gas

Many Faces of Centaurus A Sydney July 2009

13 14


PPMLR simulation code
Based upon Godunov method of numerical hydrodynamics Piecewise Parabolic Method with Lagrangian remap (PPMLR) and Riemann solver Originated from VH1 code (University of Virginia and University of Nth Carolina) Added cooling of thermal gas Code for correcting numerical shock instabilities
Many Faces of Centaurus A Sydney July 2009 13 14


Jet + Disk simulations (Sutherland & GB 2007, ApJS, 173)
Description of the ambient cloudy medium Log-normal density distribution ­ affects the porosity of the medium Kolmogorov power-law of density in Fourier space Both arise naturally in a turbulent medium

Many Faces of Centaurus A Sydney July 2009

Mean density that of an almost Keplerian disk supported vertically by thermal and supersonic turbulent pressure.

14 15


Initial mean density

Many Faces of Centaurus A Sydney July 2009

15 16


Initial mean density

Many Faces of Centaurus A Sydney July 2009

15 16


Initial mean density
2-component dark + luminous matter potential

Many Faces of Centaurus A Sydney July 2009

15 16


Initial mean density
2-component dark + luminous matter potential

Many Faces of Centaurus A Sydney July 2009

15 16


Initial mean density
2-component dark + luminous matter potential

Many Faces of Centaurus A Sydney July 2009

15 16


Parameters of jet and ISM
Relativistic equivalent
-3 43 -2

Scale = 1 kpc M LK n T
hot hot cl cl

= 26 = 2 в 10 = 2.8 в 10 ergs s cm
-1



=

=

5 c2 = 10 4p

= 8.4 в 10 = 10 cm = 10 K
4

-2

n Ї T

= 1.2 в 107 K
-3

Many Faces of Centaurus A Sydney July 2009

16 17


Jet and large scale disk
log (density)

Resolution = 5123
Many Faces of Centaurus A Sydney July 2009 17 18


Jet and large scale disk
log (density)

Resolution = 5123
Many Faces of Centaurus A Sydney July 2009 17 18


Jet and large scale disk
log (density) Evolutionar y phases:

Resolution = 5123
Many Faces of Centaurus A Sydney July 2009 17 18


Jet and large scale disk
log (density) Evolutionar y phases: Flood and channel

Resolution = 5123
Many Faces of Centaurus A Sydney July 2009 17 18


Jet and large scale disk
log (density) Evolutionar y phases: Flood and channel Pseudo-spherical energydriven bubble

Resolution = 5123
Many Faces of Centaurus A Sydney July 2009 17 18


Jet and large scale disk
log (density) Evolutionar y phases: Flood and channel Pseudo-spherical energydriven bubble Rapid jet breakout

Resolution = 5123
Many Faces of Centaurus A Sydney July 2009 17 18


Jet and large scale disk
log (density) Evolutionar y phases: Flood and channel Pseudo-spherical energydriven bubble Rapid jet breakout Classical radio galaxy phase

Resolution = 5123
Many Faces of Centaurus A Sydney July 2009 17 18


Pole-on view

Looking into the eye of the Vulcano

Many Faces of Centaurus A Sydney July 2009

18 19


Pole-on view

Looking into the eye of the Vulcano

Many Faces of Centaurus A Sydney July 2009

18 19


Radio morphology and dynamics

Synchrotron emissivity:
Many Faces of Centaurus A Sydney July 2009 19 20


Radio morphology and dynamics

Synchrotron emissivity:
Many Faces of Centaurus A Sydney July 2009 19 20


Comparison of adiabatic and radiative clouds - Jackie Cooper PhD thesis
Adiabatic

Radiative

Many Faces of Centaurus A Sydney July 2009

32 21


Comparison of adiabatic and radiative clouds - Jackie Cooper PhD thesis
Adiabatic

Radiative

Many Faces of Centaurus A Sydney July 2009

32 21


Comparison of adiabatic and radiative clouds - Jackie Cooper PhD thesis
Adiabatic

Radiative

Many Faces of Centaurus A Sydney July 2009

32 21


Hierarchy of scales (Saxton et al. 2005)

Many Faces of Centaurus A Sydney July 2009

22


That's it!

Many Faces of Centaurus A Sydney July 2009

23