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