Anisotropies
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Anisotropies. Peter Kasper Pierre Auger Director’s Review December 2011. Outline. Point Sources UHECR Anisotropy AGN Correlation Centaurus A Multiplets Neutron Astronomy Large Scale Anisotropy. Significance.

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Anisotropies

Anisotropies

Peter Kasper

Pierre Auger Director’s Review

December 2011


Outline

Outline

  • Point Sources

    • UHECR Anisotropy

      • AGN Correlation

      • Centaurus A

      • Multiplets

    • Neutron Astronomy

  • Large Scale Anisotropy


Significance

Significance

  • Pinpointing even one UHECR source would have a huge impact on the quest to understand the acceleration mechanism

  • Possibility of UHECR astronomy

  • Discriminate and refine magnetic field models

  • Provides valuable information on composition


Agn correlation

AGN Correlation

  • Evidence for 3⁰ correlation with AGN’s within 75 Mpc

  • If real then correlating events are most likely protons

  • At current level will take 10 yrs to reach 5-sigma

  • Fermilab group is investigating the apparent change

(33±5)%

Total: 28/84

P=0.006


Centaurus a

Centaurus A

  • Excess of events within 18⁰ of Centaurus A

    • 14/105 events observed

    • 4.9 expected from isotropy

    • Only 1/36 since Jan 2010


Centaurus a analysis

Centaurus A Analysis

  • With reasonable assumptions about cosmic ray acceleration and propagation processes ..

    • A correlation with Fe nuclei at energy E implies a correlation with p’s at energy E/26

    • Lemoine and Waxman; JCAP 11 (2009) 9.

  • No low energy signal seen

  • Therefore correlating events are not Fe

  • Work performed by former Fermilabpostdoc., Fred Kuehn


Multiplets

Multiplets

  • Clusters of events correlated in energy

  • Powerful tool if discovered

    • Possibility of reconstructing source direction

    • Lot of information about intervening magnetic fields and/or composition

  • Currently Auger has a 12-plet with a chance probability of 6%

  • A 24-plet would have a chance probability of 10-5

  • Fermilab group members Carlos Escobar and Carlos Hojvat are working on this


Neutron sources

Neutron Sources

  • A way to locate Galactic sources

    • Protons accelerated to high energy at source

    • Transfer their energy to neutrons via high cross-section charge exchanges processes

    • Relativistic neutrons not deflected by magnetic fields

  • Auger limits are already constraining models of EeV galactic sources

  • Fermilab group is not working on this


Large scale anisotropy

Large Scale Anisotropy

  • Predictions for and limits on the Rayleigh amplitude of an equatorial dipole

    • C-G Xgal: Compton-Getting effect

    • A/S: Streaming in Asymmetric/Symmetric Galactic magnetic fields

    • Gal: Diffusion from a Galactic source

Best upper limits

< few %

are from Auger


Large scale anisotropy1

Large Scale Anisotropy

  • Many reasons to expect a strong signal if protons are a large component

  • The Auger limits at 1 EeV are particularly surprising

  • Auger has a hint with data near 3 EeV

  • 4 more years of data to confirm

  • Fermilab group is not working on this


Summary

Summary

  • Lack/weakness of observed anisotropies is surprising

  • It is natural to expect p’s to dominate

    • Most abundant element

    • Heavy nuclei are expected to be broken apart in the accelerating environment

  • If they do then there should be significant anisotropy


Summary1

Summary

  • But perhaps UHECR’s are really dominated by heavy nuclei

    • If demonstrated, this would result in a new paradigm for cosmic ray acceleration and propagation models

  • Important to clarify the situation

    • improved statistics (x2 would help a lot)

    • Important to study data quality

      • Fermilab group is actively investigating


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