Physical conditions in potential UHECR
accelerators
Sergey GureevAstronomy Dept., Moscow State University
Ksenia PtitsynaPhysics Dept., Moscow State University
Sergey TroitskyInstitute for Nuclear Research, Moscow
1. Constraints on astrophysical accelerators:
• “Hillas plot”
• radiation losses
2. Particular sites: “Auger” AGN
• manifold of active galaxies
• an important detail of the Auger correlations
• correlated objects
important experimental updates
for specific mechanisms
from powerful BL Lacs to low-power Seyferts and LINERS
how to calculate the chance probability?
CAN THEY ACCELERATE PROTONS TO UHE?
1. Constraints on astrophysical accelerators:
• “Hillas plot”
• radiation losses
2. Particular sites: “Auger” AGN
• manifold of active galaxies
• an important detail of the Auger correlations
• correlated objects
important experimental updates
for specific mechanisms
from powerful BL Lacs to low-power Seyferts and LINERS
how to calculate the chance probability?
CAN THEY ACCELERATE PROTONS TO UHE?
Constraints on astrophysical accelerators:“Hillas plot” + radiation losses
(electrodynamics)
Assumption:• particle is accelerated by electromagnetic forces
inside an astrophysical accelerator
General limitations:• geometry
• radiation losses
energetic particles leave the accelerator
accelerating charges radiate and loose energy
geometry: the Hillas criterion:Larmor radius < size of accelerator(otherwise lefts the accelerator)
<ZBRmaximalenergy
charge magneticfield
size of theaccelerator
Schluter & Biermann 1950Hillas 1984
model-independent
Hillas 1984
the (original) Hillas plot
Boratav et al. 2000
radiation losses:rate of gain < rate of loss
synchrotron curvature
radiation losses:rate of gain < rate of loss
synchrotron curvature
depend on the mechanism
Limitations due to radiation losses: disagreement on their importance?
• protons can be accelerated “to (3-5)×1021 eV … At energies ≥ 1022 eV the cosmic ray primaries have to be heavy nuclei” Aharonyan et al. 2002
• “Practically, all known astronomical sources arenot able to produce cosmic rays with energies near few times 1020 eV” Medvedev 2003
Different acceleration regimes:
• diffusive (shocks)
• inductive (one-shot)
- synchrotron-dominated losses- curvature-dominated losses
Different acceleration regimes:
• diffusive (shocks)
plot: Medvedev 2003
gets a hit from time to time,radiates synchrotron continuously
Different acceleration regimes:
• diffusive (shocks)gets a hit from time to time, radiates synchrotron continuously• inductive (one-shot)
- synchrotron-dominated losses- curvature-dominated losses
Different acceleration regimes:
• inductive (one-shot)
plot: Medvedev 2003
is accelerated and radiates continuously
Different acceleration regimes:
• diffusive (shocks)gets a hit from time to time, radiates synchrotron continuously• inductive (one-shot)is accelerated and radiates continuously
- synchrotron-dominated losses- curvature-dominated losses
general fieldconfiguration
Different acceleration regimes:
• diffusive (shocks)gets a hit from time to time, radiates synchrotron continuously• inductive (one-shot)is accelerated and radiates continuously
- synchrotron-dominated losses- curvature-dominated losses
general fieldconfiguration
specific fieldconfiguration
Different acceleration regimes:
• diffusive (shocks)gets a hit from time to time, radiates synchrotron continuously• inductive (one-shot)is accelerated and radiates continuously
- synchrotron-dominated losses- curvature-dominated losses
general fieldconfiguration
specific fieldconfiguration
E || B(close to ablack hole)
updated Hillas plots (plus radiation constraints)- diffusive acceleration
updated Hillas plots (plus radiation constraints)- inductive acceleration, synchrotron losses
updated Hillas plots (plus radiation constraints)- inductive acceleration, synchrotron losses
updated Hillas plots (plus radiation constraints)
1. Constraints on astrophysical accelerators:
• “Hillas plot”
• radiation losses
2. Particular sites: “Auger” AGN
• manifold of active galaxies
• an important detail of the Auger correlations
• correlated objects
important experimental updates
for specific mechanisms
from powerful BL Lacs to low-power Seyferts and LINERS
how to calculate the chance probability?
CAN THEY ACCELERATE PROTONS TO UHE?
Auger correlations with AGN
- the “AGN” term is misleading
- 20% of galaxies show nuclear activity
- luminosity, size, mass scatter by orders of magnitude
- powerful BL Lacs and radio galaxiesvs. low-power Seyferts and LINERs:
quite different positions on the Hillas plot!
Auger correlations with AGN:
various AGN on the Hillas plot
Auger correlations with AGN: an important detail
how to calculate the chance probability?
list of sources list of events
• calculate number of pairs “source-event” in data• compare with expected from Monte-Carlo• estimate the chance probability
Auger correlations with AGN: an important detail
how to calculate the chance probability?
list of sources list of events
number of pairs “source-event”:what if there are several sources for one event?
2. “Correlation function”: count every pair
1. “Nearest neighbour”: one source for one event
Auger correlations with AGN: an important detail
how to calculate the chance probability?
2. “Correlation function”: count every pair
1. “Nearest neighbour”: one source for one event
formal chance probability ~10-9
number of tries ~104
chance probability ~10-5
formal chance probability ~10-4
number of tries ~104
chance probability ~1
Black hole neighbourhood:physics gouverned by the black hole mass
• (safe) upper limit on B
• size occupied by the field
measure black hole mass
estimate size
constrain field
estimate maximal energy
measure black hole mass
acceleration near black hole: no proton acceleration
possible for iron, but huge deflection in GMF(no chance to correlate at 3 degrees)
extended structures (jets, lobes)?
- detected in 7 of 17 sources- extremely low power- no model-independent B measurements- equipartition: proper place on the Hillas plot- no proton acceleration- Cen A lobes may accelerate light nuclei
Conclusions:
• updated constraints on the UHECR accelerators
• AGN=plausible accelerators
• these are NOT low-power “Auger” AGN! but powerful BL Lacs and radio galaxies
• “Auger” AGN cannot accelerate protonsto observed energies
• they can accelerate iron, but no correlations then!
• Cen A = low-power radio galaxy, can accelerate medium-charge nuclei
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