physical conditions in potential uhecr accelerators sergey gureev astronomy dept., moscow state...

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