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Angela V. Olinto The University of Chicago

Anisotropies at the Highest Energies. Angela V. Olinto The University of Chicago. CMB vs UHECR Anisotropies. UHECRS are Charged, should ‘point’ above ~ 10 EeV Z. . R L = kpc Z -1 (E / EeV) (B /  G ) -1 R L = Mpc Z -1 (E / EeV) (B / n G ) -1 where EeV= 10 18 eV.

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Angela V. Olinto The University of Chicago

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  1. Anisotropies at the Highest Energies Angela V. Olinto The University of Chicago

  2. CMB vs UHECR Anisotropies

  3. UHECRS are Charged, should ‘point’ above ~ 10 EeV Z  RL = kpc Z-1 (E / EeV) (B / G)-1 RL = Mpc Z-1 (E / EeV) (B / nG)-1 whereEeV=1018 eV weak deflection E > 1019eV strong deflection Halo B? E < 1018eV Milky way B ~ G kpc Extra-galactic B? B < nG 10 kpc

  4. Ecm = PeV (Euhecr /ZeV)1/2 (2A)1/2 2. Cosmic RaySpectrum is Power law Non-thermal Phenomena Extreme Accelerators Emax > 1020 eV E-2.7 32 orders of magnitude E-3.1 Ankle (1 particle /km2 yr) Tevatron RHIC LHC 12 orders of magnitude Swordy ‘02

  5. 3. ‘Pointing” UHECRS E ~ 100s TeV CM knee ankle

  6. 4. No known mechanism acceleration nor clear Counterparts E = Ze B L 10% efficiency 1020eV Protons 1020eV Iron GRBs LHC Log B(G) others Log L(cm)

  7. 5. Extragalactic propagation GZK imprint Cosmologically Meaningful Termination GZK Cutoff Greisen, Zatsepin, Kuzmin 1966 p+cmb +  p + 0  n +  + Proton Horizon ~1020 eV

  8. Attenuation length e+e–  Attenuation length Interaction length

  9. 6. GZK Effect  Anisotropies  Spectral Feature + LSS  Anisotropic Sky Distribution Charged Particle Astronomy!!!

  10. GZK Horizon - Protons Allard, AO, Parizot 08

  11. Horizons: 1019 eV ~ 1 Gpc Gpc 100 Mpc 1020 eV < 100 Mpc

  12. Inhomogeneous Galaxy Distribution 2MASS - Two Micron All Sky Survey

  13. Horizons: Distance Indicator !!!! the Ability to Determine Source Distribution and Point to Nearby Sources! 1019 eV ~ 1 Gpc Gpc 100 Mpc 1020 eV < 100 Mpc

  14. Southern site The Pierre Auger Observatoryof Ultra-High Energy Cosmic Rays Northern site > 400 PhD scientists from > 70 Institutions and 18 countries 20 000 km2 Argentina Australia Brasil Bolivia* Croatia* Czech Rep. France Germany Italy Mexico Netherlands Poland Portugal Slovenia Spain UK USA Vietnam* *Associate Countries 3 000 km2

  15. 18 Countries 70 Institutions, > 400 scientists

  16. Many Candidates to win the World Cup 2010!!!

  17. Auger South 1660 tanks = 3,000 km2 Surface Array 4 Fluorescence Detector Sites Science Data since 2004 Completed in June 2008

  18. surface detector

  19. tanks aligned seen from Los Leones

  20. 4 Fluorescence Detector Sites

  21. 20 May 2007 E ~ 1019 eV 1st - 4 Fold Hybrid Event

  22. > ~1 degree “astronomy” @ 50 EeV Statistical 14% @ 50 EeV Systematic 22% Less than 1 degree @ 50 EeV

  23. Observed Spectrum showns GZK GZK

  24. Unclear Trend in Observed Composition

  25. Anisotropy Analysis

  26. Auger Anisotropy Result 2007 Highest energy cosmic rays have an anisotropic distribution! Data: 27 events above 57 EeV from 1/1/2004 to 31/8/2007 (exposure of 8890 km2 sr y) Correlation with z < 0.018 AGNs in the 12th Véron-Cetty/Véron catalogue The observed correlationdid not identify the CR sources but established anisotropy at 99% c.l.

  27. Auger 2007 Anisotropy Result 3.2o- 27 highest energy event * - VCV AGN catalogue Blue shades: equal integrated exposure

  28. Challenges of the Analysis: 1. LOW STATISTICS!!!!!2. Choice of catalogs Véron-Cetty / Véron, 12th Edition, 2006 “This catalogue should not be used for any statistical analysis as it is not complete in any sense, except that it is, we hope, a complete survey of the literature.”

  29. Significance of the anisotropy result Not an “AGN correlation” result! 1st step: search for correlations between arrival directions of UHECR and various source catalogues (data from 2004/01/01 to 2006/05/27) Very large “raw significance” found w/ 12th VCV catalogue of AGNs Even after generous penalty factors for a posteriori searches and scanning of parameter space Did not seem to be fluctuation Auger collaboration set up a prescription for future data Most significant a posteriori “correlation signal”: 3.2 expected from isotropic distribution 12 out of 15 events E > 56 EeV closer than 3.1° from an AGN in 12th VCV with z ≤ 0.018 (D ≤ 75 Mpc)

  30. Exploratory scan (Period I): 1 Jan 2004-27 May 2006 Integrated exposure: 4390 km2 sr y Scan in ψ(angular distance between CR and AGN), Eth (CR energy), zmax (AGN distance) Scan implemented to find the minimum of the binomial probability P that ≥ k out of N events correlate by chance Minimum value of P: Eth = 56 EeV ψ = 3.1o zmax = 0.018 12/15 events correlate (3.2 expected by chance, p(z, ψ) = 0.21) Scan  proper penalization difficult to calculate  Prescription adopted p(z, ψ)= exposure-weighted chance probability for a CR to fall within ψ of the sources

  31. 3 Parameter Scan z ≤ 0.018 E ≥ 56 EeV  ≤ 3.1° (D ≤ 75 Mpc)

  32. Energy Threshold makes sense correlation is most significant above E = 56 EeV where the CR flux drops…

  33. Significance of the anisotropy result 2nd step: predefine a region in the sky of excess CR flux & test if next UHECRs come from this region 21% chance from isotropic distribution Independent data set, prescribed parameters, unambiguous significance Nearby VCV AGN 21% sky

  34. Independent data (Period II): 27/5/2006-31/8/2008 Integrated exposure: 4500 km2 sr y A-priori fixed parameters: Eth = 56 EeV ψ = 3.1o zmax = 0.018 8/13 events correlate (2.7 expected by chance) Probability to happen by chance from an isotropic flux: P≈1.7 10-3 Test built to have 1% probability to incorrectly reject isotropy. Test passed: 99% c.l. anisotropy Note: it does not show that VCV AGN are UHECR sources!

  35. First 27 events Exploratory scan – 12/15 events correlated (3.2 expected) Prescription passed when 8/13 correlated (2.7 expected) NOTE: original set became 14 events when reconstructed with new energy analysis, 14+13 = 27 

  36. References Science 318 (2007), 939 “Correlation of the highest energy cosmic rays with nearby extragalactic objects” Astroparticle Physics 29 (2008), 188 “Correlation of the highest-energy cosmic rays with the positions of nearby active galactic nuclei” arXiv:0906.2347 31st International Cosmic Ray Conference, Lodz , Poland, July 2009 “Astrophysical Sources of Cosmic Rays and Related Measurements with the Pierre Auger Observatory” NEW Update to come soon...

  37. ICRC Update 2009 ICRC new data (Period III): 27/5/2006-31/3/2009 after exploratory period (II+III) integrated exposure: 12650 km2sr y Updated event reconstruction: 56 EeV  55 EeV 31 new events E > 55 EeV: 44 post-prescription events A-priori fixed parameters: Eth = 55 EeV ψ = 3.1º zmax = 0.018 mask = cut out Galactic Plane

  38. ICRC 2009 Likelihood ratio: binomial probability of correlation over binomial probability in isotropic case (piso=0.21) 17/44 events in correlation (P=0.006) Isotropy still rejected at 99% c.l.

  39. Time Ordered Degree of correlation (p=k/N) pdata=17/44=0.38±0.07 Correlation degree decreased wrt our previous report but still more than 2 s.d. from isotropy

  40. A Posteriori Analysis Point source searches Different methods & Catalogs (w/ ICRC 2009 Data): I. Cross-correlation II. Log-likelihood III. 2-fold correlation Laura Watson: Bayesian Methods applied to 2007 data Fred Kuehn: Methos used in the collaboration

  41. Centaurus A

  42. Centaurus A Integral number of events vs angular distance from Cen A KS test: 2% of isotropic realizations have a maximum departure from isotropy ≥ the maximum observed departure Maximum excess @ 18o radius: 12 observed events vs 2.7 expected

  43. Other (Better) Catalogs 1. X-ray AGNs in 22-months SWIFT-BAT catalogue (261 objects) 2. Galaxies in the HIPASS survey (3058 galaxies, radio, flux-limited, HI sources) 3. HIPASS-HL: sub-sample of HIPASS (the 765 most luminous galaxies) 4. Galaxies in the 2MRS compilation (|b|>10¡, 23000 most luminous galaxies from 2MASS, full-sky, IR)

  44. Cross Correlation Measures the excess of pairs within a given angular separation wrt isotropy (departures are larger if CRs correlate with denser regions of the catalogues) e.g.: volume selected galaxies (D<200 Mpc) from 2MRS (1940 obj) No weight by distance or luminosity (equal contribution to CR flux from every source)

  45. Smoothed Maps from Catalogs For each catalogue: Smoothed probability maps of arrival directions Weight catalogue sources by flux x GZK attenuation 2 free parameters: smoothing angle σ and isotropic background (catalogue incompleteness + lower en. spill) Fc(n) = density map value in the direction n Use data to find the best values of (σ, fiso) by maximizing the LogLikelihood Parameters weakly constrained

  46. Likelihood Test Simulate 104 samples with the same number of data as in the real set Draw events according to catalogue density map or isotropically Compare the likelihood distributions with the value obtained from data Better agreement with Catalog models vs Isotropy LL sensitive to data points “in or out” of high density catalogue regions Simulated data sets based on isotropy (I) and Catalog models (II) compared to data (black line/point).

  47. 2-fold correlation method Complementary method to test overall proportionality between models and data Based on the computation of two coefficients: correlation (test match between models and data) and concentration (test clustering properties of data) Data compatible with all the models The map based on SWIFT gives the most discriminant test against isotropy

  48. Conclusions up to 3/31/2009, exposure 17,000 km2sr.y, 58 CRs w E>55 EeV Update on the correlation with VCV objects (a-priori analysis) Isotropy rejected at 99% c.l. Degree of correlation lower than in early data A-posteriori analysis: Excess of events close to Cen A (?) Distribution of arrival directions compatible with several catalogs that trace the distribution of nearby extra-galactic matter X-rays AGNs (e.g., SWIFT-BAT) interesting correlations More statistics needed to discriminate possible source scenarios “Only” collect ≈ 2 UHECR/month Only look in the Southern Sky

  49. Auger North 10 yr Black – 2MASS catalog z<0.02 Blue – Auger North simul Data – energy proportional to circle size Red – Auger South Data

  50. NEED MUCH HIGHER STATISTICS!!!! The poorest, but very energetic! THANKS!!! — Particle Physics Seminar: Auger results on UHECRs —

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