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Anisotropies

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

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  1. Anisotropies Peter Kasper Pierre Auger Director’s Review December 2011

  2. Outline • Point Sources • UHECR Anisotropy • AGN Correlation • Centaurus A • Multiplets • Neutron Astronomy • Large Scale Anisotropy

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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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