Relativistic jets in Active galactic nuclei

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A NEW EVOLUTION SCENARIO OF COMPACT SYMMETRIC
OBJECTS
Grown up FR IIs
Baby CSOs
How ?
Nozomu Kawakatu (NAOJ)
Collaborator Hiroshi Nagai (NAOJ) and Motoki
Kino (JAXA)
VSOP-2 Symposium2007, Sagamihara, Japan, 3-7
Dec. 2007
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Compact symmetric objects (CSOs)
Hot spot
Radio lobe
120 kpc
Radio
FRII radio galaxies
Similar morphology!
The origin of CSOs
However, evolutionary tracks are poorly
understood so far.
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Connection between CSOs and FR II sources
Evolution of hot spot radius is linked with the
dynamical growth of radio sources.
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A Dynamical model of Hot spots
NK Kino 2006, MNRAS, 370,1513
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A model of hot spot evolution
VHS is controlled by growth of Ah .
Cocoon dynamics
(e.g., Begelman Choiffi 1989 Kino NK 2005)
Eq. of motion (jet axis)
Eq. of motion (sideways)
Energy eq.
Vc 4Aclh /3 cocoon volume Pc cocoon
pressure ?c specific heat ratio of plasma
inside cocoon
Connection between hot spots and cocoon 1D shock
junctions
Strong deceleration leads to the strong sideways
expansion.
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Evolution of hot spot properties
The slopes of hot spot properties are functions
of X and a as follows.
Hot spot radius
Hot spot velocity
Aspect ratio of cocoon
observed rHS-lh diagram ? Constraint of hot spot
evolution
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Deceleration and acceleration ofhot spots
velocity
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Constant velocity scenario or Constant aspect
ratio ?
We test (i) the constant velocity model and (ii)
the self-similar model (Rconst.).
(e.g., Readhead et al. 1996)
(e.g., Begelamn 1996)
Forbidden region
Both simple evolutionary models can be ruled out !
The slope of ambient medium inside galaxies is
steeper than that of outside galaxies, i.e., a
gt2.2 (lh lt 1 kpc) and a lt 0.7 (lh gt 1 kpc), but
unrealistic !
Self-similar model (Rconst.) can not explain the
observed rHS-lh relation.
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A new evolution scenario of radio galaxies
Forbidden region
observation rHS ( lh gt 1 kpc)
The hot spots accelerate outside galaxies (lh gt 1
kpc) assuming a1.5 (typical value for
cluster-scale).
Inside galaxies (lh lt 1 kpc), the hot spots
decelerate in flatter density profile (a lt 0.5).
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Evolution of hot spot velocity
Our solution
CSOs
FRIIs
We predict that the advance velocity of 1 kpc
scale radio sources (MSOs) are much smaller that
of CSOs and FRII sources.
In order to test our predictions, it is important
to evaluate vHS of MSOs !
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Summary
We propose a new evolution scenario of CSOs,
comparing the observed rHS-lh
diagram with our theoretical model.
( NK, Nagai, H., Kino, M. in preparation )
We predict that the advance speed of hot spots
and lobes show the deceleration phase (lh lt 1
kpc) and the acceleration phase (lh gt 1 kpc).
In order to test our predictions, it is
essential to estimate the advance speed of hot
spots of 1 kpc scale radio sources by VLBI
observations.
acceleration
deceleration
cocoon
1 kpc
10 pc
100 kpc
By using high resolution VLBI observations with
VSOP-2, it is possible to estimate the hot spot
velocity and radius for ultra CSOs ( 1 pc).
These will impact on the evolution of radio
sources and connection with sub-pc scale jets.
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Thank you for your attention!
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Sample
FRII 3CR caatalogue (Hardcastle 98 Fernini93
Bridle 94 Gilbert) MSOs (Dallacasa 02
Fanti95 Sanghera05) CSOs (Readhead96
Taylor00 Wang03 Polatidis03 Maness04
Nagai06)
Total 106 sources.
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Evolution of hot spot luminosity
The luminosity of CSOs and MSOs are almost
equivalent to that of FRII sources.
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Discussion Fate of baby radio galaxies
CSOs
FRIIs
MSOs
VSPO-2
Sound velocity (ambient medium)
e.g., Hardcastle 2002
Only CSOs with high vHS can evolve into powerful
FRII radio galaxies, other CSOs may evolve kpc
sclae low pwer compact and/or FRIs.
(e.g., Drake et al.2004 Giroletti et al. 2007)
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VLBI
VLBI with VSOP-2
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Evolution of cocoon morphology
Forbidden region
observation rHS ( lh gt 1 kpc)
Constraints from numerical simulations
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Comparison with numerical simulations
2D relativistic hydro. Simulation in a uniform
ambient medium (a0) (Scheck et al. 2002)
density
a0 (flat ambient matter), X1.0
a0 (flat ambient matter), X1.2

Our model can describe the flow and cocoon
behavior very well.
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Prospects for VSOP-2
Hot spot radius vs. projected linear size
Distribution of the advance speed of hot spots
106 sources
hot spot radius rHS kpc
0.430.08
1.340.24
Ultra CSOs
Sub-pc jets
1 pc or lt 1 pc
First Energy dissipation 1D phase ? 2D phase
linear size lh kpc
H.Nagai (thesis)
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Appendix
Forbidden region
deceleration
R increases
acceleration
observation
R decrease
Numerical simulation
Cocoon head growth (observations) gt cocoon head
growth (simulations)
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Ingredients in powerful radio galaxies (FRIIs)
End points of AGN jets Hot spot radio
lobe
Hot spot
Radio lobe
Cocoon is consist of the shocked plasma escaped
from hot spots.
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Outline A model of hot spot evolution
The evolution of hot spot is tightly linked to
that of cocoon.
The velocity of cocoon head and hot spot is
determined by
radio lobe
cocoon head

• effective working surface
• Ah ( gt Aj ) growth
• Sideways escape
• vortex via shocks
• Jittering of jet
• etc

Ah
vh vHS
jet
hot spot
1D shock conditions (to connect the quantities
along the jet axis, i.e., jet hot spot
ambient medium)
ambient medium
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Contents

• Compact symmetric objects (CSOs)
• Connection between CSOs and powerful radio galaxy
  (FRIIs)
• Dynamical model of hot spots in AGNs
• Deceleration and acceleration of hot spot
  velocity
• Summary