Astroparticle Physics: Arrival Directions, AGN Correlation, GZK Effect

1. Astroparticle Physics Paul Sommers Penn State Brookhaven, January 29, 2008

3. Equal Exposure Plot Arrival Directions for E>3 EeV +25 deg 0 deg -30 deg -60 deg RA = 0 deg

4. Arrival directions of the 27 highest energy events

5. Veron-Cetty AGNs (red dots) Supergalactic Plane (blue line) Swift x-ray galactic black holes (blue circles)

6. Mollweide Projection With AGN marks shaded by exposure

7. Full-Sky Aitoff Projection (Observatory exposure shaded)

8. The exploratory discovery of the AGN correlation Harari et al., May, 2006 3-parameter search scan: minimum energy, circular window radius, maximum redshift for sources.

9. The GZK energy threshold For anisotropy is where the spectrum Is falling rapidly

10. GZK Horizon Definition: The distance for which 90% of the cosmic rays above an energy cut should be produced within a volume around us with that distance as radius. Depends on the fraction (90% horizon in this example) Depends on the energy cut Depends on the source energy spectrum (steepness and maximum energy) Normally assumes homogeneous source distribution The steeply falling source spectrum makes for a short horizon distance above the threshold for GZK energy loss. (Particles must start with higher energy at larger distances to arrive above the detection energy cut, but the sources do not produce many particles above those higher energies.)

12. Firm Conclusions Cosmic rays do not arrive isotropically. The arrival pattern proves that sources are extragalactic. The GZK effect is confirmed. [Spectral steepening is not due simply to “sources running out of steam.” We see structure for D<75 Mpc without confusion from more distant sources.] Extragalactic B-fields are weak enough that they do not mask the structure. Galactic halo B-fields are weak enough that they do not mask the structure. Tentative Conclusions Discrete sources out to ~75 Mpc are being detected. Charged particle astronomy will be possible with very large exposure. Halo B-fields are weak. (Point sources smeared less than 3.2 degrees.) Intergalactic B-fields are interestingly weak. The highest energy cosmic rays are protons. Cosmic ray acceleration occurs where supermassive black holes are accreting matter.

13. Outline AGN correlation Observatory description Hadronic interactions in air showers Energy spectrum Photon limits Neutrino limits In development: HEAT AMIGA Radio detectors Auger North

14. Auger Water Cherenkov Detector Solar panel and electronic box GPSantenna Commantenna Three 8” PM Tubes Battery box White light diffusing liner De-ionized water Plastic tank

20. The Auger Collaboration Argentina Australia Bolivia Brazil Czech Republic France Portugal Slovenia Spain United Kingdom United States Vietnam Germany Italy Mexico Netherlands Poland Jim Cronin Alan Watson

21. Jan 28, 2008

22. Air showers develop faster than expected for protons at high energies.

23. Universality: The electromagnetic signal depends only on energy and the grammage distance of shower maximum from the ground. Muon lateral distribution and attenuation with slant depth have little dependence on primary particle or interaction assumptions. (Only the normalization is sensitive to those.) By studying the dependence of signal on zenith angle at fixed energy (fixed intensity), the muonic contribution can be separated (on average) from the electromagnetic part. The electromagnetic signal tells the energy. This method gives systematically higher energies than the air fluorescence measurements. (Roughly 25%) The inferred muon content is higher than expected even for iron showers.

24. Auger Energy Spectrum

25. Spectrum with multiplicative factor

26. Gamma rays develop deeper in the atmosphere

27. 16% upper limit derived using measure depths of maximum in hybrid mode.

28. Signal risetime and shower front curvature are different for gamma ray showers

29. 2% upper limit at 10 EeV using surface detector shower measurements

30. Earth Skimming  Pierre Auger Neutrino Observatory Auger exposure to tau Neutrinos zenith angle ~ 90-92o  

32. Outline AGN correlation Observatory description Hadronic interactions in air showers Energy spectrum Photon limits Neutrino limits In development: HEAT AMIGA Radio detectors Auger North

33. Auger North + Auger South 5-year Auger Full-Sky Simulation ( E > 1019 eV and < 60o ) 36000 arrival directions Relative exposure as function of sin(declination)

34. Exposures in AGASA units 1 AGASA = 1630 km2·sr·yr South + North Auger North Auger South

35. The Auger North site is a 3-hour drive from Denver International Airport. Major city is Lamar, pop. 10,000 1300 meters above sea-level. Flat topography. Semi-arid or dry climate. 84 miles 84 by 48 miles is one concept, 4000 square miles 48 miles

36. Summary There is anisotropy correlating with extragalactic structure GZK effect confirmed independent of source spectrum assumptions Intergalactic magnetic fields are not strong Charged particle astronomy is coming. We need Auger North! Some reasons to suppose energies are underestimated (~25% ?) The apparent GZK horizon is more appropriate at 80 EeV than 60 EeV AIRFLY measurements suggest lower fluorescence yield Surface measurements (with universality arguments) suggest it Hints of interesting hadronic interactions at high energies Proton “beam” Xmax values stop rising with energy Muon richness is greater than predicted by extrapolations

37. Thank you! Visit www.auger.org for other information: Scientific and technical papers Event displays (1% of the data) Google Earth and Google Sky stuff [Thanks to Stephane Coutu for those]