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

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

• Vasiliki Pavlidou for Group Auger _at_ U.
  ChicagoM. Ave, L. Cazon, J. Cronin, J. de Mello
  Neto, F. Ionita, A. Olinto, V. Pavlidou, B.
  Siffert, F. Schmidt, T. Venters

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Outline

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

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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)

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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
E1020eV Blt10nG Rgt11Mpc
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Charged Particle Astronomy II

• Hope isotropic background goes away at highest
  energies
• At highest energies E1020eV GZK ? horizon ?
  only nearby sources accessible ? strong
  deviations form isotropy?

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Charged Particle Astronomy II

• Hope isotropic background goes away at highest
  energies
• At highest energies E1020eV 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

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UHECRs the questions

• Highest energy particles (gt 1018 eV)
• Spectrum?
• Protons, heavier nuclei, photons?
• Top-down or bottom-up?
• Local or cosmological?
• Sources?

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Detecting UHECRs
Credit Cosmus team (http//astro.uchicago.edu/cos
mus)
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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
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Astronomy with Auger

• Hybrid experiment (fluorescence telescopes
  surface detector array)
• better energy determination
• better exposure determination
• better arrival direction reconstruction
  (typically lt1)

Credit Cosmus team (http//astro.uchicago.edu/co
smus)
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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
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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

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Auger Highest-energy Sky Map
The Pierre Auger Collaboration
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Is The Map Anisotropic?

• The search using data between 01Jan 2004 and 26
  May 2006
• Correlation of EgtEmin events with VC catalog AGN
  of zltzmax within ? degrees. Optimize (Emin,
  zmax, ?) to maximize deviation from isotropy
• The prescription
• FIX test parametersEmin 56EeV, zmax0.018,
  ?3.1degrees
• accumulate new data. Terminate test when
  probability of isotropy to have yielded new data
  lt 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 lt1
• Combining old new data, accounting for trials
  over the 3 parameters
• False positives occur only once every 105
  isotropic realizations

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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

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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 naturesmost
  powerful accelerators, their physics, and their
  energy sources
• Map the Galactic/intergalactic magnetic field!

B. Siffert
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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

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BONUSsampling the sky with few events
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