correlation of the uhecr with agn using the new statistical test methods and the updated data from...
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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.
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