Radio Quiet AGNs as possible sources
of UHECRs
Based on work by
Asaf Pe’er (STScI),
Kohta Murase (Yukawa Inst.) & Peter Mészáros (PSU)
Phys. Rev. D, submitted
October 2009
What do we know about sources of UHECRs ?
Acceleration time <~ dynamical time•
3 1017
E
B
 20 G
r
Z
Likely
Extra-Galactic
2


E
 LB  B L  2 10 45 2 3 2  20  erg/s  1012 Lsun
 Z 
Within the
GZK horizon
No anisotropy towards galactic center•
Acceleration time <~ synchrotron cooling time •
4
A
 B  41 3 E -220 G
Z
B-field at the acceleration site
is not more than few G
Zq = charge ; Amp = mass
1  1
“Acceleration efficiency”
“Classical” sources
Restrictive limitation on source Luminosity:
2


E
LB  B L  2 1045 2 3 2  20  erg/s  1012 Lsun
 Z 
•Gamma-ray Bursts (GRBs, transient)

~ 102.5, Lg~ 1051 erg/s  L/2 >1012 Lsun
•(Radio loud) Active Galactic Nuclei (AGN, Steady):
~ 101, L~1045-1046 erg/s ; few brightest
But - Non at d<dGZK 
* “Dark” (proton only) AGN
* “Giant flares” L~ 1014 LSun , Dt~1month flares
UHECR composition
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Bellido+09
Unger+07
PAO results hint towards heavy composition at very high energy
-> Releases the Luminosity requirement
2


E
2
 LB  B L  2 1045 2 3 2  20  erg/s = 2.5 1042 Z /26 erg/s
 Z 
Heavy nuclei -> many more plausible sources !
Energy loss channels of energetic heavy nuclei
Photo-pair production: N + g -> N+ e+ e- .1
th ~ 1MeV ; ~5*10-31(Z2/A) cm2
Photo-pion production: N + g -> N + 0 .2
th ~ 145 MeV ;  ~7*10-29 cm2
Nuclear spallation .3
tsp-1 = spnc ; depend on the number density
Photo-disintegration (most important) - depends on photon spectrum .4
th ~ 10 MeV ;
c
t  2
2g A
1
dis


 th
 ' / 2g A
 ' A (') (')d'

n('')
d''
2
''
Spectra of radio quiet AGNs
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QuickTime™ and a
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MRK586
Elvis + 94
Richards+06
Approximate spectrum as broken power law, n()~0 (<1013 Hz)
n()~-2 (>1013 Hz)
Survival condition for photo-disintegration
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t
1
dis

c
2g A2


 th
 ' / 2g A
 ' A (') (')d'

n('')
d''
2
''
1
t dyn t dis
 1 r  2 1016 A1.214  2 Lob
43 cm
Fe : r  3 1018 cm

Conclusion: heavy nuclei survive photo-disintegration if
acceleration occurs on pc-scale
Observations: weak, pc-scale jets in RQ AGNs
VLBA obs. of NCG3079
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(Middelberg+07)
VLBA image of NGC4151
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(Ulvestad+05)
Shock waves expected on this scale !
(Possible
acceleration sites)
Efficiency in UHECR production
Observed flux: •
J(>1019.5 eV) ~ 5*10-16 m-2 s-1 sr-1
GZK horizon -•
similar for heavy nuclei and protons, ~100 Mpc
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erg
ÝUHECR 10
Total energy prod. rate -• 
Mpc 3 yr
44
Density of RQ AGNs in local universe -•
 42~10-3 Mpc-3 (10X RL AGNs)
Energy prod. rate of UHECRs in a single source - •
ÝUHECR /
Ý1%

(Dermer, ICRC07)
ÝUHECR  10 39.5 erg/s

Energetically consistent
Consequences
No / weak correlation 
between arrival direction of UHECRs
and radio loud AGNs (but not excluded !)
Dominate process - photodisintegration ;
- No copious production of ’s ;
- No strong ’s signature from RQ AGNs
Heavy nuclei composition: 
- hint towards AGNs sources
(disfavors GRBs)
Summary
Heavy nuclei composition of UHECRs opens window to new sources
RQ AGNs are plausible sources of UHECRs, 
provided acceleration occurs at ~pc scale.
- Consistent with recent observations of weak jets.
Energy requirement: ~1 % for UHECRs; 
Main energy loss channel - photodisintegration
- No copious production of ’s
No strong correlation with RL AGNs
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