Physical conditions
in potential UHECR
accelerators
Sergey Gureev
Astronomy Dept., Moscow State University
Ksenia Ptitsyna
Physics Dept., Moscow State University
Sergey Troitsky
Institute for Nuclear Research, Moscow
1. Constraints on astrophysical accelerators:
• “Hillas plot”
important experimental updates
• radiation losses
for specific mechanisms
2. Particular sites: “Auger” AGN
• manifold of active galaxies
from powerful BL Lacs to low-power Seyferts and LINERS
• an important detail of the Auger correlations
how to calculate the chance probability?
• correlated objects
CAN THEY ACCELERATE PROTONS TO UHE?
1. Constraints on astrophysical accelerators:
• “Hillas plot”
important experimental updates
• radiation losses
for specific mechanisms
2. Particular sites: “Auger” AGN
• manifold of active galaxies
from powerful BL Lacs to low-power Seyferts and LINERS
• an important detail of the Auger correlations
how to calculate the chance probability?
• correlated objects
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
energetic particles leave the accelerator
•
radiation losses
accelerating charges radiate and loose energy
geometry: the Hillas criterion:
Larmor radius < size of accelerator
(otherwise lefts the accelerator)
model-independent
maximal
energy
E<ZB
R
charge
size of the
accelerator
magnetic
field
Schluter & Biermann 1950
Hillas 1984
the (original) Hillas plot
Hillas 1984
Boratav et al. 2000
radiation losses:
rate of E gain < rate of
synchrotron
E loss
curvature
radiation losses:
rate of E gain < rate of
E loss
depend on the mechanism
synchrotron
curvature
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 are
not 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 field
configuration
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 field
configuration
specific field
configuration
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 field
configuration
specific field
configuration
E || B
(close to a
black 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”
important experimental updates
• radiation losses
for specific mechanisms
2. Particular sites: “Auger” AGN
• manifold of active galaxies
from powerful BL Lacs to low-power Seyferts and LINERS
• an important detail of the Auger correlations
how to calculate the chance probability?
• correlated objects
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 galaxies
vs. 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?
1. “Nearest neighbour”: one source for one event
2. “Correlation function”: count every pair
Auger correlations with AGN:
an important detail
how to calculate the chance probability?
1. “Nearest neighbour”: one source for one event
formal chance probability ~10-9
number of tries ~104
chance probability ~10-5
2. “Correlation function”: count every pair
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 protons
to observed energies
• they can accelerate iron, but no correlations then!
• Cen A = low-power radio galaxy, can accelerate
medium-charge nuclei