Active Galactic Nuclei and UHECRs

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Active Galactic Nucleiand UHECRs

• Silvano Massaglia
• Università di Torino

CRIS 2008
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Overview

• AGNs general properties
• Jets from AGNs
• Possible sites of UHECRs acceleration from
• AGNs
• Summary

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Normal Galaxies

• Stars and interstellar gas contribute to the
• radiation emission, predominantly in the
  optical band.
• The spectrum shows absorption lines by
• stars and emission by HII regions.

NGC 4750 (Kennicut 1992)
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Normal Galaxies

• Typically, ? 1011 stars of a galaxy like the
• Milky Way emit a luminosity of ? 1044 ergs s-1
  
• About 99 of the galaxies of the Local Universe
  are normal galaxies

Spectral Energy Distribution (SED) of a normal
galaxies
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Active Galaxies

• About 1 of the galaxies of the Local
• Universe show
• Strong and broad
• emission lines,
• consistent with
• velocity dispersion
• of several thousand
• kilometers per second
• for the emitting gas

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Active Galaxies

• Non-thermal emission extending from
• the radio to the X-rays and gamma bands

SED of Cen A (Prieto et al. 2007)
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Normal vs Active Galaxies
Spectral Energy Distributions
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Active Galaxies
The dominant contribution to the total
luminosity is not from stars but from an Active
Nucleus
R ? 30 kpc R ? 2 kpc
R ? 10-5 kpc
M87
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AGN Zoology

• Seyfert 1 galaxies (Sey 1) (BLR, ? 104 km/s)
• Seyfert 2 galaxies (Sey 2) (NLR, ?103 km/s)
• Radio Quiet Quasars (QSOs)
• Radio galaxies
• Radio Quasars
• BL Lac Objects
• Optically Violent Variables (OVVs)

Radio quiet AGNs No jets
Radio loud AGNs Jets
Radio loudness parameter RL5GHz/LB(nuclear)?10
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The AGN Unified Model
Accretion onto a SMBH through an accretion disk,
with possible jet ejection seen at differen
angles
(Urry Padovani, 1995)
Obscuring torus
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core of galaxy NGC4261
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Modelling the origin of AGN jets
MHD numerical simulations (Zanni et al. 2007)
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Accretion and jets
Correlation found between the accretion onto BH
and the jet kinetic power (Allen et al. 2006,
Heinz et al. 2007, Balmaverde et al. 2008)
(Jet power from Heinz Sunyaev 2003)
Radio quiet
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Radio Loud AGNs Radio Galaxies
Synchrotron Radio to X-rays
Radio emission Synchrotron F(?) ? ?-? ? ?
0.5 Electron power law distribution n(E) ?
E-p p2?1
Pictor A (z0.035) Nucleus to hot-spot ? 270
kpc jet ? 120 kpc
Radio synchrotron X-rays synchrotronSSC
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Radio Galaxies Main facts
What we observe

• Radio luminosity 1039-1044 ergs s-1
• Size a few kpc some Mpc
• Morphologies
• Polarization degree about 1-30

What we derive (but do not know for sure!)

• Life timescale 107-108 ys
• Magnetic field 10 103 ?G
• Kinetic power 1042-1047 ergs s-1
• Jet Mach number Mgt1
• Jet velocity possibly relativistic
• Jet density 10-5-10-3 cm-3
• Jet composition e-p vs e-e-(?)

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Radio Galaxies Main facts
Why these uncertainties in constraining the
basic parameters?
Absence of any line in the radiation spectrum!

• Parameters are constrained by indirect means
• Magnetic field by minimum energy
• condition (equipartition)
• Kinetic power work done against the ambient
• Jet Mach number indication of shocks
• Jet velocity jet one-sidedness
• Jet density jet numerical modelling

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Observed morphologies The Fanaroff-Riley
classification
FR II or lobe dominated (classical doubles)
FR I or jet dominated
3C 31 VLA

Active Nuclei
3C 98 VLA
FR II only have Hot-spots!
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• FR I Jet dominated emission, two-sided jets,
• found in rich clusters, weak-lined galaxies,
• less powerful
• FR II Lobe dominated emission, one-sided
  
• jets, isolated or in poor groups, strong
• emission lines galaxies, more powerful

Radio vs optical luminosities LR ?
Lopt 1.7 (Owen Ledlow 1994) Environment plays
a role?
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Possible sites of UHECRs acceleration
Active Nucleus all AGNs
Hot-spot FRII radio sources
Jet Radio loud AGNs
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UHECR Acceleration in Hot-Spots
Fermi mechanism (diffusive shock acceleration
(e.g. Drury 1983)) Emax k Z e B R ? c K1, ?
1 (optimal acceleration) Emax 1018 Z B?G Rkpc
eV ? 1021 eV Spectral distribution n(E) ? E-?,
? ? 1.5-3
UHECRs from the radio galaxy hot-spots?
(Biermann Strittmatter 1987)
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Numerical simulation of FR II jet
Supersonic and Underdense jet We use the
(M)HD code PLUTO, based on high resolution
shock-capturing schemes. (http//plutocode.to.as
tro.it)
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Hot-spot of FR II Sources from jet simulations
bow-shock
Contact discontinuity
backflow
Mach disk
intergalactic gas
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Who and Where are they?
15 FR II radio galaxies within 130 Mpc (z0.03)
and 9 within 100 Mpc (z0.024)
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Acceleration - in remote FR-II?
Distribution on the sky of FR-II galaxies located
within 130Mpc
(Lemoine, CRIS 2008)
highest energy PAO event E (1.48 ? 0.27) ?
1020 eV
(not counting the systematic uncertainty on
energy calibration 22)
closest FRII NGC4261, PKS1343-60, separation
30? closest blazar (with identified z)
TEX0554534, separation 115?
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Acceleration in jetsinductive acceleration
Acceleration of protons from E1018 eV up
to Egt1019 eV (Blanford 2000, Lyutikov Ouyed
2007) by electric field induced in sheared,
relativistic magnetized jets, whenever The
resulting particle spectrum becomes asymptotically
? E-2
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Inductive acceleration in jets
Observations of limb-brightened emission
B2 114435
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Inductive acceleration in jets
Interpretation presence in jets of a fast
central spine surrounded by a slow layer
r
z
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Acceleration in radio lobes
Magnetic force-free fields are generated by
dynamo processes in accretion disks around
SMBHs in AGNs nuclei (Colgate Li
2008) Acceleration of CRs is obtained by
electric fields, parallel to the magnetic
fields, produced by reconnection of f-f fields
in radio lobes.
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Acceleration in jets and lobes
These mechanisms require the presence of a jet
Radio-loud AGN About 100 radio-loud AGNs can be
found located within 100 Mpc from us (Mauch
Sadler 2007) Possibility of looking for
statistical correspondence between AGN locations
and arrival directions of UHECRs
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Summary

• UHECRs may be accelerated in AGNs by a variety of
  mechanisms
• The acceleration can be at work in different
  sites of the AGN
• Possible correlations between arrival directions
  and different kind of AGNs can shed light on the
  UHECRs origin