Searching for Correlations between HiRes Stereo Events and Active Galactic Nuclei

1. Searching for Correlations between HiRes Stereo Events and Active Galactic Nuclei Gordon Thomson Rutgers University

2. Outline • Introduction • HiRes stereo data • AGN’s from the Veron-Cetty catalog • Comparisons with the Auger correlation signal • Search in HiRes data

3. Introduction • Auger published a Science paper describing the correlation between their events and AGN’s from the Veron-Cetty catalog, 12th Ed. • Their correlation signal was maximized for the following parameter set: • Log(Emin) = 19.75 • zmax = 0.018 • θmax = 3.1º • This set of parameters is self-consistent. • The parameters were determined from a scan using ½ of their data, then they used the other half to test the correlation. • In the second half, 8/13 events were correlated, with random expectation = 2.7 events. • We tested our data with these parameters. • We are scanning our data to find the best parameter set, and the strength of the correlation.

4. HiRes Stereo Data • We used Bill Hanlon’s reconstruction with cuts for anisotropy, not spectrum determination (looser bracketing). • 6636 events resulted. • Bill used a consistent set of dE/dx(s) and <dE/dx> values, so his energy scale is 10% lower than HiRes 1 mono (as it should be).

5. Exposure and Spectrum • Bill calculates an exposure for this data set of 3200 km2 sr yr. • His spectrum is above the HiRes mono spectra. • This is not consistent. • His exposure must be low by 10-20%.

6. AGN Catalog • We used the Veron-Cetty catalog, 12th Ed. • They may have used QSO’s as well as AGN’s, since they plotted them on their sky map. • We did not use QSO’s.

7. Comparing the Energy Scales • For energies above log(E) = 19.75, • Auger sees 28 events with exposure of 9000 km2 sr year. • HiRes sees 13 events with exposure of 3200-4000 km2 sr year. • Auger events/exposure = 3.1±0.6 per 1000 km2 sr year. • HiRes events/exposure = 3.2±0.9 - 4.1±1.1 per 1000 km2 sr year. • The whole HiRes range is consistent with Auger. • What is the energy scale difference? • Auger has a nonlinearity since they see E-2.6 above the ankle, rather than E-2.8 • Auger nonlinearity raises their energy scale at higher energy. • Bill Hanlon’s energy scale is 10% lower than mono.  The energy scales are pretty much the same. In any case we cannot determine the difference.

8. HiRes Result at the Auger Point • We found 2 events correlated out of 13, with 3 expected randomly; i.e., no effect is seen in our data. • Peter Tinyakov and Igor Tkachev checked our numbers and agree exactly. • JAJM sent us the Auger analysis of AGASA, and no particular correlations are seen. • Add together HiRes + Auger data: 10 correlated events out of 26, with 6 expected randomly: a 1σ effect.

9. Scan in Emin around Auger Point

10. What do the HiRes Data (alone) Tell Us? • Divide the data into two random halves (actually throw random numbers), scan on first half, test with second. • This is the same procedure as Auger followed, so we have to do it too. • In addition we are scanning our half1, half2, and whole data sets, to determine chance probabilities including statistical penalties.

11. Conclusions • The HiRes data do not confirm the Auger finding of correlations with AGN’s. • The HiRes data have equal statistics to the Auger test sample. • The “world’s data” show a 1σ effect. • Stay tuned for more results in a day or two. • Our draft has been sent far and wide.