1. APS April Meeting – St. Louis April 14, 2008 Search for Correlations between HiRes Stereo Events and Active Galactic Nuclei Lauren Scott for the HiRes Collaboration Rutgers, the State University of New Jersey (submitted to Astroparticle Physics, April 2008 astro-ph/0804.0382)

2. Outline Introduction The Véron-Cetty Véron catalog Results from the Auger Collaboration Three methods for determining the significance of correlations with AGN (including statistical penalties) parameters : {θ max, E min, z max } 1. Testing HiRes data using Auger criteria 1. Testing HiRes data using Auger criteria 2. Searching two independent data sets 2. Searching two independent data sets 3. Finley-Westerhoff search of entire data set. 3. Finley-Westerhoff search of entire data set. Auto-correlation Auto-correlation Only random correlations with AGN Only random correlations with AGN No hints of anisotropy No hints of anisotropy APS April Meeting – St. Louis April 14, 2008

3. Introduction Active Galactic Nuclei (AGN) considered one of the more likely sources for ultrahigh energy cosmic rays. more likely sources for ultrahigh energy cosmic rays. When searching for correlations with AGN: When searching for correlations with AGN: 1. E min – UHECRs should have relatively straight 1. E min – UHECRs should have relatively straight trajectories. trajectories. 2. θ max – Intervening B-fields are unknown 2. θ max – Intervening B-fields are unknown 3. z max – Closest AGN should be the brightest 3. z max – Closest AGN should be the brightest (avoid GZK cutoff). (avoid GZK cutoff). APS April Meeting – St. Louis April 14, 2008

4. Véron-Cetty Véron Catalog (12 th edition) Full catalog ~108,000 sources – very uneven across the sky 22000 AGN, 85000 QSO, 550 BL-Lac APS April Meeting – St. Louis April 14, 2008

5. Véron-Cetty Véron Catalog (12 th edition) Full catalog, redshift z < 0.1 ~4900 sources 4700 AGN, 185 QSO, 1 BL-Lac (Cen A) APS April Meeting – St. Louis April 14, 2008

6. Véron-Cetty Véron Catalog (12 th edition) Average fraction of events correlated randomly in isotropic simulated events randomly in isotropic simulated events with same statistics as HiRes with same statistics as HiRes above 56 EeV as a function of θ max above 56 EeV as a function of θ max and z max. and z max. 2% correlate at θ < 1º and z < 0.01 2% correlate at θ < 1º and z < 0.01 96% correlate at θ < 10º and z < 0.10. 96% correlate at θ < 10º and z < 0.10. Random correlations overwhelm real Random correlations overwhelm real correlations over most of the range correlations over most of the range of θ max and z max. of θ max and z max. APS April Meeting – St. Louis April 14, 2008

7. Auger Result {θ max = 3.1º, E min = 56 EeVz max = 0.018 } {θ max = 3.1º, E min = 56 EeV, z max = 0.018 } Scan set : 12 / 15 (expect 3.2)Test set : 8 / 13 (expect 2.7) P = 0.0017 APS April Meeting – St. Louis April 14, 2008 Abrahams et al., Science 318, 938 (2007)

8. Method I HiRes result at the “Auger point” Full HiRes data set : 2 / 13 events above 56 EeV (expect 3.2) P = 83% No Effect {θ max = 3.1º, E min = 56 EeVz max = 0.018 } {θ max = 3.1º, E min = 56 EeV, z max = 0.018 } APS April Meeting – St. Louis April 14, 2008 Cen A M87

9. Method II Two independent scans HiRes stereo data : 6636 events with 10 17.4 < E < 10 20.1 eV. Divide randomly into two data sets (each with 3318 events). Divide randomly into two data sets (each with 3318 events). Find number of correlated events, n, at each grid point in the Find number of correlated events, n, at each grid point in the data {θ max, E min, z max } data {θ max, E min, z max } 1 st half : find the “critical point” in {θ max, E min, z max } 1 st half : find the “critical point” in {θ max, E min, z max } find fraction of simulated sets with n or more find fraction of simulated sets with n or more correlations : P data (θ max, E min, z max ) correlations : P data (θ max, E min, z max ) Find lowest chance probability : P min = P data (θ c, E c, z c ) Find lowest chance probability : P min = P data (θ c, E c, z c ) 2 nd half : analyze the data at P data (θ c, E c, z c ). 2 nd half : analyze the data at P data (θ c, E c, z c ). Chance probability at the P data (θ c, E c, z c )in the 2 nd half Chance probability at the P data (θ c, E c, z c ) in the 2 nd half is the total chance probability, including statistical penalty is the total chance probability, including statistical penalty for scan. for scan. APS April Meeting – St. Louis April 14, 2008

10. Method II Scan of 1 st half of data Scan θ max : 0.1º - 4.0º (0.1º bins) θ max : 0.1º - 4.0º (0.1º bins) E min : 19.05 - 19.80 (0.05 decade bins) E min : 19.05 - 19.80 (0.05 decade bins) z max : 0.010 - 0.030 (0.001 bins) z max : 0.010 - 0.030 (0.001 bins) Critical point {1.7º, 10 19.2 eV, 0.020} Critical point {1.7º, 10 19.2 eV, 0.020} 20 / 97 20 / 97 25 / 5000 simulated sets with 20 or 25 / 5000 simulated sets with 20 or more correlations (chance prob. 0.5%) more correlations (chance prob. 0.5%) APS April Meeting – St. Louis April 14, 2008

11. Method II Optimum point in 2 nd half Critical point {1.7º,10 19.2 eV, 0.020} Critical point {1.7º,10 19.2 eV, 0.020} 14 correlated out of 101 events 14 correlated out of 101 events 741 / 5000 simulated sets with 14 or 741 / 5000 simulated sets with 14 or more correlations, P = 15.0% more correlations, P = 15.0% (the statistical penalty for the scan: ~30) (the statistical penalty for the scan: ~30) No effect No effect APS April Meeting – St. Louis April 14, 2008

12. Method III Scan over entire data set Use method of Finley & Westerhoff, Astropart. Phys 21, 359 (2004) (2004) Scan over the entire data set (in the same way as we did for Scan over the entire data set (in the same way as we did for the first half). the first half). Find the critical point in the same way, calculating chance Find the critical point in the same way, calculating chance probability (P min ). probability (P min ). Create 5001 MC sets. Treat each of the first 5000 simulated Create 5001 MC sets. Treat each of the first 5000 simulated sets as data, comparing each to the other 5000 sets. sets as data, comparing each to the other 5000 sets. Scan entire grid in {θ max, E min, z max } and find the lowest Scan entire grid in {θ max, E min, z max } and find the lowest chance probability (P i min ). chance probability (P i min ). Count the MC sets for which P i min ≤ P min. Count the MC sets for which P i min ≤ P min. This gives a chance probability, including all statistical This gives a chance probability, including all statistical penalties for the scan. penalties for the scan. APS April Meeting – St. Louis April 14, 2008

13. Method III P min 36 / 198 correlated 9 / 5000 simulated sets with 36 or more correlations (0.18%) {θ max = 2.0º, E min = 10 19.2 eVz max = 0.016 } {θ max = 2.0º, E min = 10 19.2 eV, z max = 0.016 } Cen A M87 APS April Meeting – St. Louis April 14, 2008

14. Method III P chance APS April Meeting – St. Louis April 14, 2008 P min distribution for simulated sets 36 correlated / 198 events 36 correlated / 198 events (P min = 0.0018) (P min = 0.0018) 1210 / 5000 simulated 1210 / 5000 simulated sets with P i min ≤ 0.0018 sets with P i min ≤ 0.0018 Pchance = 24% Pchance = 24% No effect No effect

15. Auto-correlation APS April Meeting – St. Louis April 14, 2008 Critical point (2.0º, 10 19.65 eV) Critical point (2.0º, 10 19.65 eV) (29 events) (29 events) 1 of 406 possible pairs. 1 of 406 possible pairs. 228 of 1000 simluated sets 228 of 1000 simluated sets have at least 1 pair. have at least 1 pair. Chance probability = 97% Chance probability = 97% No effect No effect

16. Conclusions All correlations with AGN are consistent with random correlations only. The most robust chance probability in our analysis is 24%. Auto-correlation : probability of measuring the observed degree of correlation in an isotropic data set is 97% for E > 45 EeV. APS April Meeting – St. Louis April 14, 2008