Correlation of the UHECR with AGN

using the new statistical test methods and the updated data

from Pierre Auger Observatory

Hang Bae Kim (Hanyang Univ.)

Collaboration with J.H. Kim

ICRC 2011, Beijing

UHECR Source Hunting Confirmation of GZK suppression in the CR energy spectrum

UHECR with E > EGZK¼ 4x1019 eV mostly come fromrelatively close (d < rGZK ¼ 100 Mpc) extragalactic sources.Arrival directions of UHECR keep some correla-tionwith the source distribution.

Assumption : The intergalactic magnetic fields are not so strong that they don’t alter significantly the trajecto-ries of UHECR with these high energies.

Why statistical analysis?

• Source identification of individual UHECR is quite difficult yet.• No. of candidate sources is much larger than No. of UHECR events.

Arrival Direction AnalysisExperiment Modeling

Observed AD Distribution Expected AD Distribution

Statistical Comparison

Probability that the observed distribution is ob-tained from the expected distribution

Test Methods• Multipole moments, 2D KS, …• KS on the reduced 1D distribution

• Astrophysical Sources• Dark Matter Decay

Simulation

Exposure Function• The detector array does not cover the sky uniformly and we must

consider its efficiency as a function of the arrival direction.• Here we consider only the geometrical efficiency.

Example: RA, DEC Distribu-tion

2D Distribution

1D Distribution

Observed Data (PAO, E≥55 EeV) Simulation Data (Isotropic)

RA Distribution DEC Distribution

Kolmogorov-Smirnov TestComparison of two one-dimensional probability distributions• Kolmogorov-Smirnov (KS) statistic

• Probability that the observed distribution is obtained from the ex-pected distribution

Cumulative probability distribution

KS statistic

Auto-Angular Distance Dist. (AADD)

clustered isotropic

Distribution of the angular distances of all paris of UHECR ADs

Distribution of the angular distances of all paris of UHECR and the point sources

Correl. Angular Distance Dist. (CADD)

correlated isotropic

Distribution of the expected flux values at UHECR arrival directions

Flux-Exposure Value Dist. (FEVD)

isotropicflux-following

Simple AGN Model Selection of UHECR

• Energy cut • We take

Selection of AGN• Distance cut• We take

Hypothesis : UHECRs are composed of two compo-nents

• AGN contribution - fraction f• Background (isotropic) contribution - frac-

tion 1-f

Notes• The fraction f depends on Ec and dc.

For uniform source distribution,

PAO-AGN

UHECR flux from AGN

For simplicity, we assume the universality of AGN: Lj=L, θsj=θs

Expected flux•Two parameters :•AGN contributionfraction f,•Isotropic componentfraction 1-f,

Simple AGN Model

UHECR Luminos-ity

Dis-tance

Smear-ing

Simulation of the simple AGN model

with f=1, θs=6° for PAO.

PAO-AGN-CADD

The cumulative probability distribution of CADD using the AGN reference set

Steep rise of CPD near µ=0 means the strong correlation at small angles.

PAO data looks more correlated with AGNs than isotropic distri-bution.

PAO data are not consistent with the hypothesis that they are completely originated from AGNs.

Adding isotropic (background) component can make the con-sistency improved.

More correlation with AGN than simple isot-ropy

Complete AGN origina-

tion is also ruled out.

Adding isotropic com-ponent makes the AGN model more plausible.

Correlation got weaker for PAO data released in 2010.

Correlation with AGNPAO

Restricting the sources … Number of AGN (Sources) >> Number of UHECR Fine classification of AGN may be need.

– Physical properties and/or Environments

Distance Binning – No physical motivation, but …

Summary

We developed the statistical methods for the com-parison of two HUECR AD distributions:AADD, CADD, FEVD, …• Isotropy• Correlation with point sources

Test of UHECR–AGN correlation• The simple AGN model

AGN contribution + Isotropic background Two parameters : AGN fraction, Smearing angle• Data

UHECR : 2010 PAO data, AGN : 13th Ed. of VCV cata-log• AGN domination with a small smearing angle is ruled out.

UHECR source hunting must be continued.