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Mapping the Ultra-high--energy Cosmic-ray Sky with the Pierre Auger Observatory

Mapping the Ultra-high--energy Cosmic-ray Sky with the Pierre Auger Observatory. Vasiliki Pavlidou for Group Auger @ U. Chicago: M. Ave, L. Cazon, J. Cronin, J. de Mello Neto, F. Ionita, A. Olinto, V. Pavlidou, B. Siffert, F. Schmidt, T. Venters. Outline.

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Mapping the Ultra-high--energy Cosmic-ray Sky with the Pierre Auger Observatory

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  1. Mapping the Ultra-high--energy Cosmic-ray Sky with the Pierre Auger Observatory Vasiliki Pavlidou for Group Auger @ U. Chicago:M. Ave, L. Cazon, J. Cronin, J. de Mello Neto, F. Ionita, A. Olinto, V. Pavlidou, B. Siffert, F. Schmidt, T. Venters

  2. Outline • Alternative messengers: the final mapping frontier • Ultra-high--energy cosmic ray astronomy • The Pierre Auger Observatory • Astronomy with Auger • Outlook

  3. not yet available… Alternative Messengers: the Final Frontier • Humanity: a pre-warp civilization • Cartography: a messenger-based enterprise • Conventional messengers: photons • Alternative messengers: • Neutrinos • Gravitational waves • Charged nuclei (cosmic rays)

  4. Low-energy cosmic ray sky S. Swordy Charged Particle Astronomy • Difficult! Deflections in B-field • Only at highest energies could deflections be small • Still… • At highest energies source fluxes extremely low • Very hard to obtain adequate statistics to resolve sources if fighting against isotropic background Rgyro = 0.11 Mpc E20/ZBG E~1020eV B<10nG R>11Mpc

  5. E. Armengaudsims by A. Kravtsov D. Allard Charged Particle Astronomy II • Hope: isotropic background goes away at highest energies • At highest energies E~1020eV: GZK  horizon  only nearby sources accessible strong deviations form isotropy?

  6. Charged Particle Astronomy II • Hope: isotropic background goes away at highest energies • At highest energies E~1020eV: GZK  horizon  only nearby sources accessible strong deviations from isotropy? • Horizon necessary but not sufficient to see anisotropies • Intergalactic B-field has to be sufficiently small! • Expectations from theory not clear-cut: • Dolag et al. (2004): Deflections small (few degrees), expect strong anisotropies • Sigl et al (2004): Deflections large (tens of degrees), anisotropies smeared

  7. UHECRs: the questions • Highest energy particles (> 1018 eV) • Spectrum? • Protons, heavier nuclei, photons? • Top-down or bottom-up? • Local or cosmological? • Sources?

  8. Detecting UHECRs Credit: Cosmus team (http://astro.uchicago.edu/cosmus)

  9. The Pierre Auger Observatory of Ultra-high Energy Cosmic Rays ~400 scientists from ~70 Institutions and 17 countries 1554 deployed 1509 filled 1464 taking data AIM: 1600 tanks, 3,000km2

  10. Astronomy with Auger • Hybrid experiment (fluorescence telescopes + surface detector array) • better energy determination • better exposure determination • better arrival direction reconstruction (typically <1°) Credit: Cosmus team (http://astro.uchicago.edu/cosmus)

  11. The highest-energy Auger spectrum Residuals from a standard spectrum -3.30 ± 0.06 -2.62 ± 0.03 - 4.1 ± 0.4 Pierre Auger Collaboration

  12. What would we look for? • GZK  No background  event  nearby source • Very few events • Does the sky look isotropic? • With very few events, very easy to get compatibility with isotropy • If incompatibility with isotropy, signal must be strong • On the other hand: with very few events,every realization of isotropy special • The Auger Collaboration anisotropies policy

  13. Auger Highest-energy Sky Map The Pierre Auger Collaboration

  14. Is The Map Anisotropic? • The search: using data between 01Jan 2004 and 26 May 2006 • Correlation of E>Emin events with VC catalog AGN of z<zmax within  degrees. Optimize (Emin, zmax, ) to maximize deviation from isotropy • The prescription: • FIX test parameters:Emin = 56EeV, zmax=0.018, =3.1degrees • accumulate new data. Terminate test when probability of isotropy to have yielded new data < 1% • The confirmation: • Data collected between 27 May 2006 and 31 August 2007 • Signal so strong it only required 8 new events to fulfill prescription • From 8 new events 6 correlate, probability to get from isotropy <1% • Combining old + new data, accounting for “trials” over the 3 parameters: • False positives occur only once every 105isotropic realizations

  15. What does this mean? • The highest-energy cosmic-ray sky is anisotropic!(sources still unclear) • Intergalactic B-field small, cosmic rays good messengers for mapping the nearby universe • Astrophysics! • UHECR source identification, study • Timely concurrent operation with gamma-ray, neutrino, and low-energy photon observatories • UHECR astronomy possible: time to build a bigger telescope! Auger North

  16. Auger North • Planned location in Colorado, US • Full-sky coverage • Optimized for operation in energies where arrival directions are anisotropic • Sufficient exposure to: • Detect individualsources • Calculate fluxes, spectra • Answer fundamentalquestions about nature’smost powerful accelerators, their physics, and their energy sources • Map the Galactic/intergalactic magnetic field! B. Siffert

  17. Conclusions • Highest-energy CR sky anisotropic • Auger South results proof-of-concept for charged particle astronomy • More data + Auger North = individual source detection, individual source fluxes, spectra…

  18. BONUS:sampling the sky with few events

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